See the healthy pregnancy weight-gain range for your pre-pregnancy BMI, based on IOM/CDC guidelines, with typical gain by week. A supportive general guide — not a target — to discuss with your provider.
Pre-pregnancy weight and height set your starting BMI category, which the guidelines use to suggest a healthy total gain. Twins and other situations follow different advice — check with your provider.
General guidance from IOM/CDC ranges, not medical advice and not a personal target. If weight or eating in pregnancy worries you, that’s worth talking through with your midwife or doctor, who can give individual, supportive guidance.
How the Pregnancy Weight Gain Calculator Works
This tool estimates a healthy total pregnancy weight-gain range based on your pre-pregnancy BMI, then breaks that range down into a typical gain-so-far figure for your current week. It follows the general IOM/CDC gain ranges by BMI category — it is a guide, not a personal target.
Formula: Pre-pregnancy BMI = weight in kg ÷ (height in meters)². Your BMI sets a category and its total recommended gain range: Underweight (BMI under 18.5) = 12.7–18.1 kg; Healthy weight (18.5–24.9) = 11.3–15.9 kg; Overweight (25–29.9) = 6.8–11.3 kg; Obese (30+) = 5.0–9.1 kg. For weeks 1–13, typical gain scales evenly from 0.5–2 kg by week 13. After week 13, typical gain = (0.5 to 2 kg) + (current week − 13) × a category-specific weekly rate, capped so it never exceeds the total recommended range.
- Units — switch between metric (kg/cm) and imperial (lb/in) for all inputs.
- Pre-pregnancy weight — your weight before pregnancy, used with height to set your starting BMI.
- Height — used together with pre-pregnancy weight to calculate BMI.
- Current week of pregnancy — (1–42) used to calculate the typical gain expected by this point.
- Current weight (optional) — if entered, compares your actual gain so far against the typical range for your week.
Example Scenarios
| Pre-pregnancy Weight & Height | Week | BMI Category | Typical Gain by This Week |
|---|---|---|---|
| 65 kg, 165 cm | 12 | Healthy (BMI 23.9) | 0.5–1.8 kg |
| 65 kg, 165 cm | 20 | Healthy (BMI 23.9) | 3.0–5.2 kg |
| 65 kg, 165 cm | 36 | Healthy (BMI 23.9) | 8.6–12.4 kg |
| 80 kg, 160 cm | 30 | Obese (BMI 31.3) | 3.4–6.6 kg |
| 45 kg, 170 cm | 42 | Underweight (BMI 15.6) | 12.7–18.1 kg |
| 90 kg, 175 cm | 25 | Overweight (BMI 29.4) | 3.3–6.0 kg |
Pregnancy Weight Gain Calculator FAQ
How is my BMI category determined for pregnancy weight gain guidance?
Your pre-pregnancy weight and height are converted into BMI (kg divided by height in meters, squared). That number sorts you into underweight (under 18.5), healthy (18.5–24.9), overweight (25–29.9), or obese (30+), each following its own IOM/CDC recommended total gain range.Why is the recommended total weight gain different for each BMI category?
Guidelines recommend more total gain for lower starting weights and less for higher starting weights, since the goal is a healthy outcome relative to where you began. This is general guidance, not a rule, and your provider can tailor it to you.Does this calculator apply if I’m pregnant with twins or multiples?
No. Twin and multiple pregnancies follow different, generally higher, weight-gain guidelines that this single-baby calculator does not use. If you’re expecting multiples, ask your provider for guidance suited to your pregnancy.What does “typical gain by this week” actually represent?
It’s a general reference point built by scaling gain evenly to about 0.5–2 kg by week 13, then adding a category-specific weekly rate afterward, capped at your total range. It’s a guide for context, not a week-by-week target to hit exactly.I entered my current weight and it says I’m above or below the typical range — should I worry?
Being a little outside the typical range at one point is common and often completely fine; the calculator simply flags it for context. If weight changes concern you, that’s a good, supportive conversation to have with your midwife or doctor.Is this calculator a substitute for what my doctor or midwife tells me?
No. It applies general IOM/CDC ranges for information only and isn’t personalized medical advice. Your midwife or doctor knows your health history and can give guidance specific to your pregnancy.Related Calculators
If you’re tracking pregnancy milestones alongside your weight gain, the pregnancy week calculator and due date calculator can help you confirm exactly where you are in your pregnancy. If you’re expecting more than one baby, see the twin pregnancy weight gain calculator for guidance suited to multiples.