Pregnancy Calculators
Browse our collection of free online pregnancy calculators — designed to support you through every stage of your pregnancy journey. From finding your due date to tracking your ovulation window, our tools give you fast, accurate, and easy-to-understand results based on standard clinical guidelines.
Our Free Pregnancy Calculators
- Pregnancy Due Date Calculator — Find your estimated delivery date based on your last period or conception date
- Pregnancy Week Calculator — Find out how many weeks pregnant you are right now
- Pregnancy Weight Gain Calculator — Track healthy weight gain by trimester based on your pre-pregnancy BMI
- Ovulation Calculator — Predict your most fertile days and ovulation window
- Conception Calculator — Estimate your conception date based on your due date or last period
How Pregnancy Dating Works
Pregnancy is typically measured in weeks starting from the first day of your last menstrual period (LMP) — not from the date of conception. This means that at the moment of conception (around week 2), you are already considered 2 weeks pregnant clinically. A full-term pregnancy lasts approximately 40 weeks from LMP, or 38 weeks from conception. Understanding this distinction helps you interpret your due date and weekly pregnancy milestones correctly.
Pregnancy Trimesters at a Glance
| Trimester | Weeks | Key Developments |
|---|---|---|
| First Trimester | Weeks 1–12 | Organ formation, heartbeat detectable around week 6, highest miscarriage risk |
| Second Trimester | Weeks 13–26 | Growth phase, movement felt, gender detectable by scan |
| Third Trimester | Weeks 27–40 | Rapid weight gain, lung maturation, preparation for birth |
How to Calculate Your Due Date
The most common method for calculating your estimated due date (EDD) is Naegele’s Rule: add 280 days (40 weeks) to the first day of your last menstrual period. For example, if your LMP was 1 January, your EDD would be around 8 October. Our Pregnancy Due Date Calculator does this instantly and also calculates your due date from a known conception date.
How to Track Your Ovulation Window
Ovulation typically occurs around 14 days before the start of your next period. For a 28-day cycle, this means ovulation happens around day 14. The fertile window — when conception is most likely — spans approximately 5 days before ovulation and the day of ovulation itself, due to sperm viability. Our Ovulation Calculator estimates your fertile window based on your cycle length and last period date.
Healthy Weight Gain During Pregnancy
The amount of weight you should gain during pregnancy depends on your pre-pregnancy BMI. Gaining too little can affect foetal growth; gaining too much increases the risk of complications like gestational diabetes and high blood pressure. General NHS and clinical guidelines recommend the following:
| Pre-Pregnancy BMI | Recommended Total Gain |
|---|---|
| Underweight (under 18.5) | 12.5–18 kg (28–40 lbs) |
| Healthy weight (18.5–24.9) | 11.5–16 kg (25–35 lbs) |
| Overweight (25–29.9) | 7–11.5 kg (15–25 lbs) |
| Obese (30 and above) | 5–9 kg (11–20 lbs) |
Frequently Asked Questions
How accurate is the due date calculator?
Due date calculations are estimates based on average cycle length and standard gestational timelines. Only around 5% of babies are actually born on their calculated due date — most arrive within two weeks either side. An early ultrasound scan remains the most accurate method of dating a pregnancy.
Can I use these calculators if my cycle is irregular?
Our ovulation and due date calculators use a standard 28-day cycle as the default but allow you to input your actual cycle length for a more personalised result. If your cycle is highly irregular, a healthcare provider or fertility specialist can offer more accurate assessment.
What week does morning sickness usually start?
Morning sickness typically begins around week 6 of pregnancy and usually peaks between weeks 8 and 10. For most women it eases by week 12–14. Use our Pregnancy Week Calculator to track where you currently are in your pregnancy.
Please note: These calculators provide estimates based on standard pregnancy timelines. Always consult your midwife or GP for personalised medical advice.
Explore Other Calculator Categories
- Health Calculators — BMI, calories, body fat, and fitness tools
- Finance Calculators — Budget for your growing family
- Time Calculators — Date and duration tools