Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Health, Fitness & Wellness
Period Calculator — Next Period Date from Cycle Length
Next period ≈ last period + cycle length days.
Project your next period from last start date and average cycle length. Estimates only—not a diagnosis or prescription.
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Inputs
2140
040
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Recommendations
Tailored to your live inputs and result—guidance only, not professional advice.
- Interpret
Treat this as a planning estimate
Primary result: Next period (approx.) = 6 days. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.
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Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Cycle length (days)
The “Cycle length (days)” value used in this tool’s formula. Adjust it to see results update live.
Days since last period
The “Days since last period” value used in this tool’s formula. Adjust it to see results update live.
How this calculator works
Project your next period from last start date and average cycle length. Estimates only—not a diagnosis or prescription. Next period ≈ last period + cycle length days. Example: 22 days since period, 28-day cycle → next period in ~6 days.
Next period ≈ last period + cycle length days.
Example: 22 days since period, 28-day cycle → next period in ~6 days.
When to use this Period
Common use cases
- Project your next period from last start date and average cycle length.
- Sanity-check with this case: 22 days since period, 28-day cycle → next period in ~6 days.
- The relationship is: Next period ≈ last period + cycle length days.
Localized examples
- Health, Fitness & Wellness: the example on this page uses the same formula as the widget.
What you get
- Fields: Cycle length (days), Days since last period
- Next period ≈ last period + cycle length days.
- Example on the page: 22 days since period, 28-day cycle → next period in ~6 days.
How to Calculate Period Step-by-Step
- 1Enter Cycle length (days), Days since last period. Use the values you have, not a catalog average, unless that is all you know.
- 2Next period ≈ last period + cycle length days.
- 3Worked case: 22 days since period, 28-day cycle → next period in ~6 days.
- 4If this number would change a drug, a diet, or a return-to-play call, take it to a clinician. The page never examined you.
Governing formula
Next period ≈ last period + cycle length days.
22 days since period, 28-day cycle → next period in ~6 days.
Example: set Cycle length (days) = 28, Days since last period = 22, then read the result.
Variable definitions
- cycleLengthDays
Cycle length (days)
The “Cycle length (days)” field. Default 28; typical range 21–40.
- daysSinceLastPeriod
Days since last period
The “Days since last period” field. Default 22; typical range 0–40.
- The formula (Next period ≈ last period + cycle length days.) does not see labs, medications, sleep, or injury history. A clinician does.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Next period ≈ last period + cycle length days.
Related calculators
Health, Fitness & Wellness
- Conception Date CalculatorBack-calculate an estimated conception window from cycle timing.
- Ovulation CalculatorPredict ovulation day and fertile window from cycle length and LMP.
- Pregnancy Due Date CalculatorEstimate due date and gestational age from days since last period (LMP).
- Pregnancy Week CalculatorConvert days since LMP into pregnancy week and trimester.
- Army Body Fat CalculatorCheck body fat against approximate Army tape-test screening limits.
- BAC CalculatorEstimate blood alcohol content from drinks, weight, and time (Widmark).
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Community
Reviews & Ratings
See what others think about this tool, then leave your own rating to help improve CalculioHub.
4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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