TempoLife › Features › Due date, ovulation and weight gain
Pregnancy tools
Three deterministic calculators built on published methods — Naegele's rule for the due date, ACOG's fertile-window guidance, and the IOM weight-gain ranges by pre-pregnancy BMI.
These are estimates for planning, built from published methods (Naegele, ACOG, IOM) — not antenatal care. Your clinician adjusts dates to your actual measurements and history; that personalised answer is the one that counts.
| Tool | What it gives you |
|---|---|
| Due date calculator | Due date, gestational age and trimester dates from the last period. |
| Ovulation and fertile window | From your cycle length, per the ACOG framing. |
| Weight-gain ranges | The IOM ranges by pre-pregnancy BMI, with the breastfeeding note. |
Sources: ACOG — methods for estimating due date · IOM / NRC 2009 — weight gain during pregnancy · checked 2026-09-03
Frequently asked questions
How is a due date calculated?
The classic Naegele rule: first day of the last menstrual period plus 280 days (40 weeks). It assumes a 28-day cycle and ovulation on day 14 — real pregnancies vary, which is why the due date is a reference point, not a deadline.
How accurate is an ovulation estimate?
It is a population-level estimate: ovulation about 14 days before the NEXT period, so cycle length minus 14. Sperm survive up to about 5 days and the egg about 24 hours, so the fertile window is roughly the 5 days before ovulation plus the day after — the ACOG framing this page uses.
How much weight should I gain in pregnancy?
The IOM ranges by pre-pregnancy BMI are on the weight-gain page: from 12.5-18 kg for underweight to 5-9 kg for obesity. The range, not the midpoint, is the guidance — and your clinician's number is the one that matters.
Nine months, one log
TempoLife keeps weight, sleep and routines in one place through the pregnancy and after — the data your midwife will love you for.