Pregnancy & baby calculators
Pregnancy and baby calculators, made calm and clear
Small, focused tools for the questions that come up between appointments. Each one shows the formula behind the number, tells you where the guidance comes from, and keeps your dates on your own device.
Choose a tool
Due Date Calculator
Estimate your baby's due date from the first day of your last period, then see your current pregnancy week, trimester and upcoming milestone dates. Includes a shareable result card.
Open tool →Ovulation Calculator
Estimate your ovulation day, your seven-day fertile window and your two peak fertility days from your cycle length, with the assumptions spelled out.
Open tool →Conception Date Calculator
Work out when you most likely conceived, from your last period or from a due date you already know, and see the week your pregnancy is dated from.
Open tool →Implantation Calculator
See the six-to-twelve-day implantation window after ovulation, the most likely day, and the earliest sensible day for a pregnancy test.
Open tool →Baby Percentile
See how your baby's weight and length compare with growth chart percentiles for their age and sex.
Contraction Timer
Time contractions and see their length and frequency so you can describe the pattern to your midwife.
Corrected Age
Adjust your premature baby's age for a fair comparison with growth and development milestones.
Guides & data
Reference tables for the questions that need a number rather than a calculator. Every range is copied from public guidance, labelled with its source, and dated so you can see when it was last checked.
Pregnancy Weight Gain Chart
Recommended total weight gain by pre-pregnancy BMI for one baby or twins, plus the weekly rate for the second and third trimesters.
View chart →Baby Feeding Chart by Age
Feeds per day, formula amounts per feed and daily totals from birth to 12 months, with breast milk and formula kept separate.
View chart →Baby Sleep Schedule by Age
Total sleep in 24 hours, night sleep and nap ranges from birth to two years, and an honest note on wake windows.
View chart →How these tools are built
Three rules apply to every calculator on Baby Tools.
- Free, no account No email, no sign-up, no paywall, no ads to dismiss before you get an answer.
- Private by design Everything runs in your browser. The dates you type are never sent to a server or stored anywhere.
- Sourced, not guessed Each tool explains its formula in plain English and cites public guidance from the NHS and ACOG. These tools are educational and never a substitute for medical advice.