Free Pregnancy & Fertility Calculators
Estimate your due date, pregnancy week, ovulation, fertile window, and more with simple free calculators.
Private by design
Every calculation runs in your browser. No account, no email, and no date you enter ever leaves your device.
Pregnancy Due Date Calculator
Estimate your due date from your last period, a conception date, or an IVF transfer. Everything is worked out in your browser.
These calculators provide estimates for informational purposes only. They are not intended to diagnose, treat, prevent, or replace professional medical advice. Pregnancy and menstrual cycles can vary, so results may not be exact.
Popular calculators
The tools people reach for most, whether you're tracking a cycle or already counting weeks.
Pregnancy Due Date Calculator
Estimate your due date from your last period, conception, or an IVF transfer.
OpenPregnancy Week Calculator
See how many weeks and days along you are today, to the day.
OpenOvulation Calculator
Estimate when you ovulate and which days are most fertile.
OpenPeriod Calculator
Project your next period and the cycles after it.
Open
Why use these calculators
Private by design
Every calculation runs in your browser. The dates you enter are never sent to a server or stored anywhere.
Fast on any phone
Lightweight pages with no sign-up, no pop-ups and nothing blocking the calculator.
Clear about limits
Every result says what it assumes and what it can't tell you. Estimates are presented as estimates.
Every calculator
Pregnancy Due Date Calculator
Estimate your due date from your last period, conception, or an IVF transfer.
OpenPregnancy Calculator
The whole picture: due date, current week, trimester and key dates.
OpenPregnancy Week Calculator
See how many weeks and days along you are today, to the day.
OpenOvulation Calculator
Estimate when you ovulate and which days are most fertile.
OpenFertile Window Calculator
A day-by-day cycle calendar showing your most fertile days.
OpenPregnancy Test Calculator
Estimate the dates when a home test could give a meaningful result.
OpenConception Date Calculator
Work backwards from your due date to estimate when you conceived.
OpenImplantation Calculator
See the days after ovulation when implantation typically happens.
OpenIVF Due Date Calculator
Precise dating from your transfer date and embryo age.
OpenPeriod Calculator
Project your next period and the cycles after it.
Open
How the numbers work
Short explanations of the arithmetic behind each estimate, and where it stops being dependable.
How is a pregnancy due date calculated?
Where the 280-day rule comes from, why pregnancy is dated from your last period, and how cycle length and ultrasound change the estimate.
Read moreHow many weeks pregnant am I?
How pregnancy weeks are counted, what 12w3d means, how trimesters are divided, and why weeks do not convert neatly into months.
Read moreHow does an ovulation calculator work?
Why ovulation is estimated by counting back from your next period, how the luteal phase makes that work, and where the method breaks down.
Read more