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Hub · Units

Unit converters that keep the dictionary honest

Each converter is a single conversion with the factor written out, a worked example, and a note about the trap — US gallons vs imperial, decimal megabytes vs mebibytes, SI kilo vs the legal inch, a cup of flour that was scooped not spooned. Nothing here uploads a file. Change the number; the result updates.

If a lab sheet, a listing, and a recipe all use the same word for different sizes, pick the page that names both sides. The reverse converter is linked when we actually built the pair.

Length & Distance

Race courses, floor plans, and hiking GPS rarely agree on the same unit. SI prefixes (ym to Ym) live on one meter grid. Legal inches, chains, rods, au, and parsecs are their own pages because those factors are not powers of ten.

  1. 1Meters to KilometersA marathon is 42,195 m → 42.195 km. A 400 m track lap is 0.4 km.
  2. 2Feet to MetersA 6 ft person is 1.8288 m. A 10 ft ceiling is 3.048 m.
  3. 3Inches to CentimetersA 32-inch TV is 81.28 cm on the diagonal. A 12-inch ruler is 30.48 cm.
  4. 4Miles to KilometersA marathon 26.2 mi is about 42.16 km. Ten miles is 16.09 km.
  5. 5Yards to MetersA 100-yard football field (playing yards) is 91.44 m. A 120-yard field including end zones is 109.73 m.
  6. 6Millimeters to InchesRain of 30 mm is 1.181 in. A 10 mm hex key is 0.394 in.
  7. 7Centimeters to Inches180 cm → 70.866 in (5 ft 10.9 in). A 30 cm school ruler is 11.81 in.
  8. 8Meters to Feet1.80 m tall → 5.905 ft. A 400 m lap is 1,312.3 ft.
  9. 9Kilometers to Miles10 km → 6.2137 mi. Official marathon 42.195 km → 26.219 mi.
  10. 10Nautical Miles to KilometersA 100 nmi leg is 185.2 km. One nautical mile is 1.852 km or about 1.151 statute miles.
  11. 11Micrometers to NanometersVisible green light ~0.55 µm → 550 nm. A 10 µm dust grain is 10,000 nm.
  12. 12Light Years to Kilometers1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
  13. 13Furlongs to MilesThe Kentucky Derby 10 furlongs = 1.25 mi. A 5 furlong race is 0.625 mi.
  14. 14Cubits to Inches4 cubits → 72 in (6 ft) on this scale. A 6-cubit staff is 108 in.
  15. 15League to Kilometers1 league → 4.828 km. 20,000 leagues → about 96,561 km (more than twice around Earth).
  16. 16SI Meter Prefix Converter5 km → 5,000 m → 5,000,000 mm. 400 nm violet light → 0.4 µm.
  17. 17Inches to Millimeters1 in = 25.4 mm. 2 in = 50.8 mm. A 12 in ruler is 304.8 mm.
  18. 18Chains to Meters1 chain = 20.1168 m. A 22-yard cricket pitch is 1 chain. 10 chains = 201.168 m.
  19. 19Rods to Meters1 rod = 5.0292 m. 4 rods = 1 chain = 20.1168 m.
  20. 20Astronomical Units to Kilometers1 au = 149,597,870.7 km. 5.2 au (Jupiter-ish) ≈ 777,908,927 km.
  21. 21Parsecs to Light Years1 pc ≈ 3.26156 ly. 10 pc ≈ 32.616 ly (a handy absolute-magnitude distance).

Weight & Mass

Kitchen scales, shipping labels, and UK stone are different dictionaries for the same kilograms. Prefix scaling stays on the gram. Troy ounces and metric carats are locked legal constants, not kilo-something.

  1. 1Kilograms to Pounds70 kg → 154.3 lb. A 20 kg suitcase is 44.1 lb.
  2. 2Grams to Ounces100 g of chocolate is 3.53 oz. A 454 g box is about 16 oz (one pound).
  3. 3Pounds to Ounces2.5 lb of apples → 40 oz. A 7.5 lb newborn is 120 oz.
  4. 4Milligrams to GramsA 200 mg caffeine cap is 0.2 g. 1,000 mg of salt is 1 g.
  5. 5Stone to Pounds12 st → 168 lb. 11 st 7 lb → 11.5 st → 161 lb.
  6. 6Metric Tons to Kilograms2.5 t of gravel → 2,500 kg. A 20 t truck load is 20,000 kg.
  7. 7Ounces to Grams8 oz of flour ≈ 226.8 g. 16 oz = 1 lb ≈ 453.6 g.
  8. 8Pounds to Kilograms150 lb → 68.04 kg. A 45 lb plate is 20.41 kg.
  9. 9Carats to GramsA 2.5 ct stone is 0.5 g. 100 ct of gem rough is 20 g.
  10. 10Atomic Mass Units to Grams12 u (carbon-12 atom) ≈ 1.993 × 10⁻²³ g. Water 18 u ≈ 2.989 × 10⁻²³ g per molecule.
  11. 11Long Tons to Pounds3 long tons → 6,720 lb. One long ton is also 1.016 metric tons.
  12. 12Short Tons to Pounds1.5 short tons of mulch → 3,000 lb. 10 tons on a scale ticket is 20,000 lb.
  13. 13Grains to Milligrams115 gr → 7,452 mg (7.45 g). 437.5 gr = 1 avoirdupois ounce.
  14. 14Slugs to KilogramsA 2-slug mass is 29.19 kg. 1 slug weighs about 32.17 lbf at standard g.
  15. 15Pennyweights to Grams5 dwt of gold ≈ 7.78 g. 20 dwt = 31.10 g (a troy ounce).
  16. 16SI Gram Prefix Converter2.5 kg → 2,500 g → 2,500,000 mg. A 200 mg tablet is 0.2 g.
  17. 17Troy Ounces to Grams1 ozt = 31.1034768 g. 10 ozt bar = 311.034768 g. ~32.1507 ozt in a kilogram.
  18. 18Carats to Milligrams1 ct = 200 mg. 0.25 ct = 50 mg. 2 ct = 400 mg.

Temperature

Weather, ovens, and lab work bounce between Celsius, Fahrenheit, kelvin, Rankine, Réaumur, and Gas Mark. The math is exact; your oven’s thermostat is not.

  1. 1Celsius to Fahrenheit0 °C → 32 °F (freezing). 100 °C → 212 °F (boiling at 1 atm). 180 °C oven → 356 °F.
  2. 2Fahrenheit to Celsius98.6 °F → 37 °C. 350 °F baking → 176.7 °C. −40 °F is −40 °C (the crossover).
  3. 3Celsius to Kelvin0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
  4. 4Kelvin to Celsius310 K (about body temperature) → 36.85 °C. 0 K → −273.15 °C.
  5. 5Fahrenheit to Kelvin32 °F → 273.15 K. 212 °F → 373.15 K. −459.67 °F → 0 K.
  6. 6Kelvin to Fahrenheit273.15 K → 32 °F. 310 K → 98.3 °F. 0 K → −459.67 °F.
  7. 7Rankine to Fahrenheit491.67 °R → 32 °F. 671.67 °R → 212 °F.
  8. 8Réaumur to Celsius80 °Ré → 100 °C. 16 °Ré cellar → 20 °C.
  9. 9Gas Mark to FahrenheitGas Mark 4 → 350 °F (177 °C). Mark 6 → 400 °F. Mark 9 → 475 °F.
  10. 10Celsius to Rankine0 °C → 491.67 °R. 100 °C → 671.67 °R.

Area & Volume

Apartment listings in m², US lots in acres, recipes in cups. US gallons, imperial gallons (4.54609 L), metric 250 mL cups, and the FDA 240 mL legal cup are named on the page that uses them.

  1. 1Square Meters to Square Feet20 m² bedroom → 215.3 ft². 100 m² house is 1,076 ft².
  2. 2Acres to Square Feet0.25 acre → 10,890 ft². 2 acres → 87,120 ft².
  3. 3Hectares to Acres5 ha → 12.36 acres. 1 ha is 2.47 acres or 107,639 ft².
  4. 4Square Kilometers to Square Miles10 km² → 3.86 mi². 1 mi² is 2.59 km².
  5. 5Square Inches to Square CentimetersLetter paper 8.5×11 in = 93.5 in² → 603.2 cm².
  6. 6Square Yards to Square MetersA 12×15 ft room is 20 yd² → 16.72 m².
  7. 7Liters to Gallons20 L of paint → 5.28 US gal. 75 L tank → 19.8 gal.
  8. 8Milliliters to Fluid Ounces30 mL shot → 1.01 fl oz. 240 mL cup → 8.12 fl oz.
  9. 9Gallons to Liters5 gal bucket → 18.93 L. 13.2 gal tank → 50.0 L.
  10. 10Cups to Milliliters1 cup milk → 237 mL. ¾ cup → 177 mL. 2 cups → 473 mL (a US pint).
  11. 11Tablespoons to Milliliters2 tbsp vanilla → 29.6 mL. 1 tbsp is roughly 15 mL on a metric spoon.
  12. 12Teaspoons to Milliliters1 tsp salt → 4.93 mL. 5 mL medicine cup ≈ 1.01 US tsp.
  13. 13Cubic Meters to Cubic Feet2 m³ of soil → 70.6 ft³. 0.5 m³ fridge is 17.7 ft³.
  14. 14Cubic Inches to Cubic Centimeters350 in³ → 5,735 cm³ (5.74 L). 1 in³ is 16.39 cc.
  15. 15Pints to Liters2 US pints → 0.946 L (a quart). 1 UK pint would be 0.568 L — different tool conceptually.
  16. 16Quarts to Liters2 qt → 1.89 L. 4 qt = 1 gal = 3.785 L.
  17. 17Fluid Ounces to Milliliters12 fl oz can → 355 mL. 1 fl oz ≈ 30 mL in kitchen talk, 29.57 in the lab.
  18. 18Bushels to Liters1 bu → 35.24 L. 40 bu → 1,410 L.
  19. 19Acres to Hectares40 acres → 16.19 ha. 1 acre → 0.405 ha.
  20. 20Square Miles to Acres2 mi² → 1,280 acres. 0.5 mi² → 320 acres.
  21. 21Imperial Gallons to Liters1 imp gal = 4.54609 L. 5 imp gal ≈ 22.730 L. An 8 gal firkin ≈ 36.369 L.
  22. 22Metric Cups to Milliliters1 metric cup = 250 mL. ½ cup = 125 mL. 2 cups = 500 mL.
  23. 23US Legal Cups to Milliliters1 legal cup = 240 mL. 4 legal cups = 960 mL (a “quart” on a label, not 946.35 mL customary).

Digital Storage & Data

Drive boxes print decimal GB. Operating systems often print GiB. The SI vs IEC scaler covers kB through EB and KiB through EiB, plus ASCII/Unicode code points and PiB vs PB.

  1. 1Megabytes to Gigabytes4,700 MB CD image → 4.7 GB. 1,000 MB → 1 GB.
  2. 2Gigabytes to Terabytes2,000 GB → 2 TB. A 500 GB SSD is 0.5 TB.
  3. 3Kilobytes to Megabytes3,000 KB → 3 MB. 500 KB is 0.5 MB.
  4. 4Bits to Bytes32 bits → 4 bytes. 8,000,000 bits → 1,000,000 bytes (1 MB decimal).
  5. 5Bytes to Kilobytes50,000 B → 50 KB. 1,024 B → 1.024 KB (or 1 KiB).
  6. 6Terabytes to Petabytes500 TB → 0.5 PB. 2,000 TB → 2 PB.
  7. 7Megabits to Megabytes25 Mbps → 3.125 MB/s. 1 Gbps → 125 MB/s.
  8. 8Gigabits to Gigabytes1 Gbps → 0.125 GB/s (125 MB/s). 40 Gbps → 5 GB/s.
  9. 9Kibibytes to Kilobytes1 KiB → 1.024 KB. 1,024 KiB = 1 MiB → 1,048.576 KB.
  10. 10Mebibytes to Megabytes1 MiB → 1.049 MB. 4,768 MiB of RAM sold as “5 GB” in mixed marketing.
  11. 11Gibibytes to Gigabytes256 GiB SSD → 274.9 GB decimal. 1 GiB → 1.074 GB.
  12. 12Tebibytes to Terabytes1 TiB → 1.100 TB. 12 TiB → 13.19 TB.
  13. 13Data Transfer Time4.7 GB at 50 Mbps → 752 s ≈ 12.5 min. 50 GB at 100 Mbps → 67 min.
  14. 14Resolution Pixel Calculator1920×1080 → 2.07 MP, 16:9. 6000×4000 still → 24 MP, 3:2.
  15. 15Audio Bitrate Storage320 kbps × 4 min → 9.6 MB. 128 kbps × 3.5 min → 3.36 MB. WAV 1411 kbps × 3 min → 31.7 MB.
  16. 16SI vs IEC Byte Scaler1 GiB = 1.073741824 GB. 1 PiB ≈ 1.1259 PB. 500 GB advertised ≈ 465.66 GiB.
  17. 17ASCII / Unicode Code PointsA → 65, U+0041, 01000001, UTF-8 41. € → 8364, U+20AC, UTF-8 E2 82 AC.
  18. 18Pebibytes to Petabytes1 PiB ≈ 1.1259 PB. 10 PiB ≈ 11.259 PB.

Time & Speed

Hours into minutes, SI prefixes on the second, knots into mph, Mach at sea-level air, Julian years in seconds, and a pace calculator if you only know the race distance and the clock.

  1. 1Hours to Minutes2.25 h → 135 min. 8 h shift → 480 min.
  2. 2Days to Hours3 days → 72 h. 0.5 day → 12 h.
  3. 3Weeks to Days6 weeks → 42 days. 0.5 week → 3.5 days.
  4. 4Years to Days1 year → 365.25 days. 4 years → 1,461 days (includes the leap average).
  5. 5Seconds to Milliseconds0.25 s → 250 ms. 1 s ping timeout → 1,000 ms.
  6. 6MPH to km/h70 mph → 112.7 km/h. 25 mph school zone → 40.2 km/h.
  7. 7m/s to km/h27.8 m/s → 100 km/h. 5 m/s jogging → 18 km/h.
  8. 8Knots to MPH25 kn sail → 28.8 mph. 5 kn drift → 5.8 mph.
  9. 9ft/s to m/s88 ft/s → 26.82 m/s (60 mph). 32.17 ft/s² is g, not this page — that is acceleration.
  10. 10Mach to MPHMach 1 → ~761 mph. Mach 0.85 airliner → ~647 mph true at this ISA number, not at 35,000 ft.
  11. 11Centuries to Years0.5 century → 50 years. 2 centuries → 200 years.
  12. 12Microseconds to Seconds1,000 µs → 0.001 s (1 ms). 1,000,000 µs → 1 s.
  13. 13Nanoseconds to Milliseconds1×10⁹ ns → 1,000 ms (1 s). 500,000 ns → 0.5 ms.
  14. 14Refresh Rate to Frame Time60 Hz → 16.67 ms. 120 Hz → 8.33 ms. 240 Hz → 4.17 ms.
  15. 15Running Pace Calculator10 km in 50 min → 5:00 /km (8:03 /mi). 42.2 km in 240 min → 5:41 /km.
  16. 16SI Second Prefix Converter250 ms → 0.25 s → 250,000 µs. 1 ns clock tick → 1,000 ps.
  17. 17Minutes to Hours90 min = 1.5 h. 45 min = 0.75 h. An 8 h shift is 480 min.
  18. 18Hours to Days24 h = 1 day. 8 h = 0.333… day. 168 h = 7 days.
  19. 19Days to Weeks7 d = 1 week. 14 d = 2 weeks. 30 d ≈ 4.2857 weeks.
  20. 20Decades to Years1 decade = 10 yr. 3 decades = 30 yr. 10 decades = 1 century on the same Julian stick.
  21. 21Millennia to Years1 millennium = 1,000 yr. 2 millennia = 2,000 yr.
  22. 22Julian Years to Seconds1 yr = 31,557,600 s. 0.001 yr ≈ 31,557.6 s (~8.77 h).
  23. 23Days to Calendar Years365 d = 1 year. 730 d = 2 years. 1,000 d ≈ 2.740 years of 365 days.
  24. 24Days to Leap Years366 d = 1 leap year. 732 d = 2. 1,461 d ≈ 3.992 leap-year lengths.

Energy, Power & Pressure

Calories that are chemistry calories or IT calories, kilowatt-hours on a bill, newton/pascal prefix grids, torr, hectopascals, and PSI versus bar on a tyre sidewall.

  1. 1Calories to Joules1 cal → 4.184 J. 1 kcal food Calorie → 4,184 J. 2,000 kcal diet ≈ 8.37 MJ.
  2. 2kWh to Megajoules10 kWh → 36 MJ. 0.5 kWh dryer cycle → 1.8 MJ.
  3. 3Horsepower to Watts1 hp → 746 W. 400 hp → 298 kW.
  4. 4BTU to kWh3,412 BTU → 1 kWh. 100,000 BTU furnace pulse → 29.3 kWh of heat energy.
  5. 5Pascals to PSI101,325 Pa → 14.70 psi. 2 bar (200,000 Pa) → 29.0 psi.
  6. 6Bar to PSI2.5 bar → 36.3 psi. 1 bar ≈ 14.5 psi vs 1 atm = 14.7 psi.
  7. 7Atmospheres to Pascals1 atm → 101,325 Pa. 10 atm → 1.013 MPa.
  8. 8Electronvolts to Joules1 eV → 1.602×10⁻¹⁹ J. 1 MeV → 1.602×10⁻¹³ J. 13.6 eV → 2.18×10⁻¹⁸ J.
  9. 9Kilowatts to Horsepower75 kW → 100.6 hp. 250 kW → 335 hp.
  10. 10Celsius Heat Units to Joules1 CHU → 1,899 J. 10 CHU → 18.99 kJ. 1 CHU ≈ 1.8 BTU.
  11. 11SI Watt Prefix Converter1.5 kW → 1,500 W → 0.0015 MW. A 5 mW laser pointer is 0.005 W.
  12. 12SI Joule Prefix Converter4.184 J → 0.004184 kJ. A 2,000 kJ snack label is 2 MJ.
  13. 13SI Newton Prefix Converter1 kN → 1,000 N. A 50 mN contact force is 0.05 N.
  14. 14SI Pascal Prefix Converter101.325 kPa → 1,013.25 hPa → 0.101325 MPa.
  15. 15Torr to Pascals760 torr = 101,325 Pa. 1 torr ≈ 133.322 Pa. 25 torr ≈ 3,333 Pa.
  16. 16Hectopascals to Pascals1013.25 hPa = 101,325 Pa. 1000 hPa = 100,000 Pa = 1 bar.
  17. 17IT Calories to Joules1 calIT = 4.1868 J. 1,000 calIT = 4,186.8 J. 1 kcalIT = 4.1868 kJ.
  18. 18Kilojoules to Joules1 kJ = 1,000 J. 4.184 kJ = 4,184 J. 100 kJ = 100,000 J.
  19. 19Newtons to Kilonewtons1,000 N = 1 kN. 9.81 N ≈ 0.00981 kN. 10,000 N = 10 kN.

Cooking & Baking

Cups of flour that are 120 g if you spooned, sticks of butter that are 113 g, Gas Mark 4 that is 180 °C, and sourdough hydration that only counts if you weigh the starter too.

  1. 1Flour Cups to Grams2½ cups AP flour → 300 g. ¼ cup → 30 g.
  2. 2Sugar Cups to Grams¾ cup sugar → 150 g. 2 cups → 400 g.
  3. 3Butter Sticks to Grams1 stick → 113 g (4 oz). 2 sticks → 227 g. Half a stick → 57 g.
  4. 4Brown Sugar Cups to Grams1 packed cup → 220 g. ½ cup → 110 g.
  5. 5Cocoa Powder Cups to Grams¼ cup cocoa → 21 g. ½ cup → 43 g.
  6. 6Honey Tablespoons to Grams2 tbsp honey → 42 g. ¼ cup (4 tbsp) → 84 g.
  7. 7Oats Cups to Grams½ cup oats → 45 g. 2 cups granola base → 180 g.
  8. 8Dry Rice Cups to Cooked1 cup dry jasmine → ~3 cups cooked. ½ cup dry → ~1½ cups cooked.
  9. 9Milk Cups to Milliliters1 cup milk → 237 mL. ¾ cup water → 177 mL.
  10. 10Yeast Packets to Teaspoons1 packet → 2¼ tsp (7 g). 2 packets → 4½ tsp.
  11. 11Salt Pinch to Teaspoons1 pinch → 0.0625 tsp. 8 pinches → ½ tsp.
  12. 12Fluid Ounces to Cups8 fl oz → 1 cup. 16 fl oz → 2 cups. 2 fl oz shot → ¼ cup.
  13. 13Quarts to Gallons4 qt → 1 gal. 2 qt → ½ gal. 1 qt → 0.25 gal.
  14. 14Pinch to Grams1 pinch → 0.36 g. A teaspoon of table salt is ~6 g, about 16 pinches.
  15. 15Gas Mark to CelsiusGas Mark 4 → 180 °C. Mark 1 → 140 °C. Mark 9 → 240 °C.
  16. 16Fahrenheit to Gas Mark350 °F → Mark 4. 400 °F → Mark 6. 275 °F → Mark 1.
  17. 17Round Pan to Square8-inch round → 7.1-inch square (use 8-inch square, slightly shallower). 9-inch round → 8.0-inch square.
  18. 18Sourdough Hydration350 g water + 500 g flour → 70%. 400 g water → 80%.
  19. 19Recipe Scaling Factor250 g flour × 1.5 → 375 g. A 9-serving stew × 2/3 → 6 servings.
  20. 20Brix to Specific Gravity12 °Bx wort → about 1.048 SG. 24 °Bx → about 1.101.

Science & Lab

Moles, lumens, radians, farads, hertz/volt/ampere/ohm prefix grids, arcminutes, milliradians, and pH. The formulas are textbook; the lab bench still has density, activity coefficients, and a probe that was not calibrated this morning.

  1. 1Moles to Grams2 mol water → 36.03 g. 0.1 mol NaCl (58.44) → 5.84 g.
  2. 2Frequency to Wavelength100 MHz → 3.00 m. 2.45 GHz → 0.122 m.
  3. 3Decibels to W/m²60 dB → 10⁻⁶ W/m². 0 dB → 10⁻¹² W/m².
  4. 4Lumens to Lux800 lm on 10 m² → 80 lx. 1600 lm on 4 m² → 400 lx.
  5. 5Foot-candles to Lux10 fc → 107.6 lx. 1 fc → 10.76 lx.
  6. 6Radians to Degreesπ rad → 180°. 1 rad → 57.296°. 2π → 360°.
  7. 7Degrees to Gradians90° → 100 gon. 180° → 200 gon. 45° → 50 gon.
  8. 8RPM to rad/s60 rpm → 6.283 rad/s (1 rev/s). 1800 rpm → 188.5 rad/s.
  9. 9Volts Amps Ohms12 V across 6 Ω → 2 A, 24 W. 5 V, 20 mA LED math is a different, kinder page.
  10. 10Farads to Microfarads0.0001 F → 100 µF. 1 µF → 0.000001 F.
  11. 11Henrys to Millihenrys0.01 H → 10 mH. 1 H → 1,000 mH.
  12. 12Webers to Maxwells1 Wb → 100,000,000 Mx. 1 µWb → 100 Mx.
  13. 13Becquerels to Curies3.7×10¹⁰ Bq → 1 Ci. 37 kBq → 1 µCi.
  14. 14Sieverts to rem1 mSv → 0.1 rem. 50 mSv → 5 rem.
  15. 15Stokes to Centistokes1 St → 100 cSt. 0.01 St → 1 cSt (water-ish).
  16. 16Poise to Pascal-seconds1 P → 0.1 Pa·s. 1 cP → 0.001 Pa·s.
  17. 17Mass Flow to Volume Flow1 kg/s of water → 0.001 m³/s (1 L/s). 1 kg/s of air at 1.2 kg/m³ → 0.83 m³/s.
  18. 18Wavelength to Photon Energy550 nm → ~2.25 eV. 1 nm X-ray-ish → 1.24 keV.
  19. 19pH to [H+]pH 3 → 0.001 mol/L. pH 7 → 1×10⁻⁷ mol/L.
  20. 20dBm to Watts0 dBm → 0.001 W (1 mW). 30 dBm → 1 W. −30 dBm → 1 µW.
  21. 21SI Hertz Prefix Converter440 Hz → 0.440 kHz. 2.4 GHz Wi-Fi → 2,400 MHz.
  22. 22SI Volt Prefix Converter5 V USB → 5,000 mV. A 230 kV line is 230,000 V.
  23. 23SI Ampere Prefix Converter20 mA → 0.02 A → 20,000 µA. A 200 A welder is 0.2 kA.
  24. 24SI Ohm Prefix Converter10 kΩ → 10,000 Ω → 0.01 MΩ. A 50 mΩ shunt is 0.05 Ω.
  25. 25SI Farad Prefix Converter10 µF → 10,000 nF → 0.01 mF. 100 pF → 0.1 nF.
  26. 26SI Henry Prefix Converter1 mH → 1,000 µH → 0.001 H. A 4.7 µH choke is 0.0047 mH.
  27. 27SI Coulomb Prefix Converter1 C → 1,000 mC. 50 µC from a piezo is 0.05 mC.
  28. 28SI Weber Prefix Converter1 mWb → 0.001 Wb → 1,000 µWb.
  29. 29SI Tesla Prefix Converter50 µT → 0.05 mT → 5×10⁻⁵ T. A 1.5 T MRI magnet is 1,500 mT.
  30. 30SI Siemens Prefix Converter500 µS/cm probe-ish number as 500 µS → 0.5 mS. Do not skip the /cm; that is a different unit.
  31. 31Degrees to Arcminutes1° = 60′. 0.5° = 30′. 360° = 21,600′.
  32. 32Degrees to Arcseconds1° = 3,600″. 0.001° = 3.6″. 1″ = 1/3600°.
  33. 33Milliradians to Degrees1 mrad ≈ 0.057296°. 17.4533 mrad ≈ 1°. A full circle is 2π×1000 ≈ 6,283.2 mrad.
  34. 34Kilohertz to Megahertz1,000 kHz = 1 MHz. 440 kHz = 0.44 MHz. 2,400 kHz = 2.4 MHz.

Design & Web

px to rem at a 16 px root, PostScript picas and twips, 72 pt per inch, 300 DPI print pixels, CSS shadows, hex, and a slug that ASCII-folds on purpose. CSS inches are not press inches.

  1. 1Pixels to Rem16 px → 1 rem. 24 px → 1.5 rem. 8 px → 0.5 rem.
  2. 2Pixels to Em16 px with 16 px parent → 1 em. 20 px with 16 px parent → 1.25 em.
  3. 3Points to Pixels12 pt → 16 px. 9 pt → 12 px. 72 pt → 96 px (one CSS inch).
  4. 4Inches to Pixels1 in at 300 DPI → 300 px. 1 in at 72 DPI → 72 px. 8.5 in letter width at 300 → 2550 px.
  5. 5Centimeters to Pixels10 cm at 300 DPI → 1,181 px. 1 cm at 96 DPI → 36 px.
  6. 6Aspect Ratio1920 wide at 16:9 → 1080 high. 1080 wide at 1:1 → 1080 high.
  7. 7CSS Box Shadow0 8px 24px 0 rgba(0,0,0,0.12) is a polite card lift.
  8. 8Hex to RGB#ffffff → rgb(255, 255, 255). #000 → rgb(0, 0, 0).
  9. 9RGB to CMYKrgb(255,0,0) → roughly 0, 100, 100, 0. Black rgb(0,0,0) → 0,0,0,100.
  10. 10HSL to Hexhsl(210, 80%, 50%) is a strong blue. hsl(0, 0%, 100%) → #ffffff.
  11. 11Percentage to Ratio16 / 100 → 4:25. 50 / 100 → 1:2. 1920 / 1080 → 16:9 if you enter those as part/whole.
  12. 12Grid Column Width1200 px, 12 cols, 16 px gap → 84 px per column. 960 / 12 / 20 gap → 65 px.
  13. 13Typography Scale16 px × 1.25 → 20, 25, 31.25… A major second (1.125) is subtler.
  14. 14Viewport Width to Pixels10 vw at 375 px wide → 37.5 px. 100 vw at 1440 → 1440 px.
  15. 15Line Height Multiplier16 px × 1.5 → 24 px. 24 px × 1.2 → 28.8 px.
  16. 16Download Time from File Size25 MB on 50 Mbps → 4 s. 700 MB on 10 Mbps → 9.3 min.
  17. 17Image Compression Ratio8 MB RAW-ish preview to 1.6 MB JPEG → 0.20 (80% smaller).
  18. 18Base64 to ImageA tiny PNG data URL begins data:image/png;base64,iVBOR…
  19. 19URL Slug Generator“How to convert meters to feet” → how-to-convert-meters-to-feet.
  20. 20Unix Timestamp to Date0 → 1970-01-01T00:00:00.000Z. 1,000,000,000 → 2001-09-09.
  21. 21Picas to Points1 pica = 12 pt. 6 picas = 72 pt = 1 in. A 12-pica column is 2 in.
  22. 22Inches to Points1 in = 72 pt. 0.5 in margin = 36 pt. 8.5 in = 612 pt.
  23. 23Twips to Points20 twips = 1 pt. 1440 twips = 72 pt = 1 in. 2880 twips = 2 in.

Everyday Sizes & Life

Shoe lasts, fuel economy that runs the wrong way from mpg to L/100km, BMI in both unit systems, Morse, and Roman numerals up to 3999.

  1. 1Shoe Size ConverterUS men 9 → EU 42, UK 8.5, ~28 cm. US women 8 → EU 39, UK 6.
  2. 2Ring Size ConverterUS 7 → ~17.3 mm diameter, ~54.4 mm inside circumference, UK N-ish.
  3. 3Clothing Size ConverterUS 8 → UK 12, EU 40. Letter M → about US 10 / EU 42.
  4. 4Bra Size Converter34B US → 34B UK, ~75B EU, ~12B AU.
  5. 5Hat Size Converter7¼ → ~22.8 in, 57.8 cm. 7½ → ~23.6 in, 59.8 cm.
  6. 6MPG to L/100km30 US mpg → 7.84 L/100km. 50 US mpg → 4.70 L/100km.
  7. 7L/100km to MPG8.0 L/100km → 29.4 US mpg, 35.3 UK mpg. 5.0 → 47.0 US mpg.
  8. 8Miles to kg CO₂100 miles → 40.4 kg at 404 g/mile. 12,000 miles/year → 4,848 kg.
  9. 9Watts and Hours to kWh1500 W kettle × 0.1 h → 0.15 kWh. 10 W router × 24 h → 0.24 kWh.
  10. 10Appliance Running Cost1500 W × 4 h × $0.16 → $0.96. 10 W USB charger × 8 h → about a penny.
  11. 11Solar Panel Daily kWh400 W × 4.5 h → 1.8 kWh. 6 kW array × 5 h → 30 kWh before losses.
  12. 12GPM to L/min2.5 gpm → 9.46 L/min. 10 gpm hose → 37.9 L/min.
  13. 13Beaufort to KnotsForce 4 → ~13 kn. Force 8 → ~37 kn. Force 0 → calm.
  14. 14Tire Size Comparison225/55R17 → sidewall 124 mm, diameter ~26.7 in.
  15. 15Gear Ratio to Speed2500 rpm, 4.10 overall, 26.5 in tire → about 48 mph.
  16. 16BMI Metric and Imperial70 kg at 170 cm → 24.2. 154 lb at 67 in → 24.1.
  17. 17Blood Sugar mg/dL to mmol/L100 mg/dL → 5.55 mmol/L. 180 mg/dL → 10.0 mmol/L.
  18. 18Cholesterol mg/dL to mmol/L200 mg/dL → 5.17 mmol/L. 100 mg/dL HDL → 2.59 mmol/L.
  19. 19Due Date from LMPLMP 1 Mar 2026 → EDD 6 Dec 2026.
  20. 20Dog Years to Human1 year → 15. 2 years → 24. 5 years → 39. 10 years → 64.
  21. 21Cat Years to Human1 year → 15. 2 years → 24. 5 years → 36. 12 years → 64.
  22. 22Roman Numerals to ArabicXIV → 14. XLII → 42. MMXXVI → 2026.
  23. 23Arabic to Roman Numerals2026 → MMXXVI. 44 → XLIV. 9 → IX.
  24. 24Morse Code to Text... --- ... → sos. hello → .... . .-.. .-.. ---
  25. 25Number Base ConverterFF hex → 255 decimal → 377 octal → 11111111 binary.

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