Pregnancy Weight Gain Calculator
See the suggested weight gain for your BMI, the range for the week you're in, and where you are now. Gentle guidance only; your midwife or doctor knows you best.
Mix any units, for example feet and inches with kilograms. Results follow the unit of "Weight now".
Today by default.
Add an earlier weight to see how fast you've been gaining lately, and where that pace would take you.
Week-by-week plan with your weights
| Week | Gain | Your weight |
|---|
How your weight gain is checked
Your numbers, step by step. Gentle guidance from the CDC and IOM ranges.
- 1
BMI before pregnancy
60 kg ÷ 1.65²
= 22.0 - 2
Your total range
Healthy weight
→ 11.3–15.9 kg - 3
Range for your week
At 24w 0d
4.9–7.7 kg - 4
Where you are
Gained 6 kg
→ on track
Read more: the ranges, the formula, a worked example and kind reminders
How much weight is healthy to gain depends mostly on your body mass index (BMI) before pregnancy. The ranges here are the US Institute of Medicine (IOM) 2009 guidelines that the CDC uses, which many countries follow. Your midwife or doctor may suggest something different for you, and their advice comes first.
The formula
BMI = weight before pregnancy in kg ÷ (height in m × height in m)
weeks 0 to 13: range = first-trimester gain × weeks ÷ 13
weeks 13 to 40: range = first-trimester gain + (total range − first-trimester gain) × (weeks − 13) ÷ 27
gained so far = weight now − weight before pregnancy
The first-trimester gain is 1.1 to 4.4 lb (0.5 to 2 kg), worked out separately for the low and high ends. The CDC gives the totals in pounds, so the sums are done in pounds and turned into kilograms (1 lb = 0.45359237 kg). For twins the straight line runs to the total at 37 weeks, when twins are often born; that's a rough guide only, as no weekly twin rates are published.
Worked example
You're 165 cm tall and weighed 60 kg before pregnancy. BMI = 60 ÷ (1.65 × 1.65) = 60 ÷ 2.7225 = 22.0, a healthy weight, so the total range is 25 to 35 lb = 11.3 to 15.9 kg. At 24 weeks you're 11 weeks past week 13, so the low end is 1.1 + (25 − 1.1) × 11 ÷ 27 = 10.8 lb (4.9 kg) and the high end is 4.4 + (35 − 4.4) × 11 ÷ 27 = 16.9 lb (7.7 kg). You weigh 66 kg now, so you've gained 66 − 60 = 6.0 kg, inside 4.9 to 7.7 kg: on track. To finish in range at 40 weeks you'd gain (11.3 − 6.0) ÷ 16 = 0.33 to (15.9 − 6.0) ÷ 16 = 0.62 kg a week from here.
Suggested total gain, one baby
| BMI before pregnancy | Total gain | A week, 2nd and 3rd trimesters (IOM) |
|---|---|---|
| Underweight (below 18.5) | 28–40 lb (12.7–18.1 kg) | 1–1.3 lb (0.44–0.58 kg) |
| Healthy weight (18.5 – 24.9) | 25–35 lb (11.3–15.9 kg) | 0.8–1 lb (0.35–0.5 kg) |
| Overweight (25 – 29.9) | 15–25 lb (6.8–11.3 kg) | 0.5–0.7 lb (0.23–0.33 kg) |
| Obesity (30 or more) | 11–20 lb (5.0–9.1 kg) | 0.4–0.6 lb (0.17–0.27 kg) |
Suggested total gain, twins
| BMI before pregnancy | Total gain |
|---|---|
| Underweight (below 18.5) | 50–62 lb (22.7–28.1 kg) * |
| Healthy weight (18.5 – 24.9) | 37–54 lb (16.8–24.5 kg) |
| Overweight (25 – 29.9) | 31–50 lb (14.1–22.7 kg) |
| Obesity (30 or more) | 25–42 lb (11.3–19.1 kg) |
* The underweight twin range comes from a 2003 study by Luke and colleagues, not the IOM. The other twin ranges are the IOM's provisional guidelines.
Extra calories
For one baby, starting at a healthy weight, the CDC says most people need no extra calories in the first trimester, about 340 extra a day in the second and about 450 extra a day in the third.
A few kind reminders
- Weight goes up and down day to day. Weigh at the same time of day, in similar clothes, and look at the trend over a few weeks.
- Many people gain little, or even lose a bit, in the first trimester because of sickness. That's common.
- Please don't diet or try to lose weight during pregnancy unless your midwife or doctor suggests it.
- BMI doesn't know your whole story. Your clinician will look at your health, your baby's growth and your scans.
For information only, not medical advice. If you're worried about your weight, or notice sudden swelling or a fast gain over a few days, contact your midwife or doctor. Total ranges checked on the CDC pregnancy weight gain page on 11 October 2026; weekly rates and the first-trimester gain are from the IOM 2009 report.
Common questions
How much weight should I gain during pregnancy?
It depends on your BMI before pregnancy. For one baby the CDC suggests 28 to 40 lb (about 12.7 to 18.1 kg) if you were underweight, 25 to 35 lb (11.3 to 15.9 kg) at a healthy weight, 15 to 25 lb (6.8 to 11.3 kg) if overweight and 11 to 20 lb (5 to 9.1 kg) with obesity. Your midwife or doctor may suggest a different goal for you.
How much weight should I have gained by now?
Most of the gain comes after the first trimester. The usual guide assumes about 1.1 to 4.4 lb (0.5 to 2 kg) by the end of week 13, then a steady rise to your total range at 40 weeks. At 24 weeks, someone who started at a healthy weight would typically have gained about 4.9 to 7.7 kg (10.8 to 16.9 lb).
How much weight should I gain each week?
In the second and third trimesters the IOM 2009 guidelines suggest about 0.35 to 0.5 kg (0.8 to 1 lb) a week at a healthy weight, 0.44 to 0.58 kg (1 to 1.3 lb) if underweight, 0.23 to 0.33 kg (0.5 to 0.7 lb) if overweight and 0.17 to 0.27 kg (0.4 to 0.6 lb) with obesity. Weekly gain goes up and down, so look at the trend.
How much weight should I gain with twins?
For twins the CDC suggests 37 to 54 lb (about 16.8 to 24.5 kg) at a healthy weight, 31 to 50 lb (14.1 to 22.7 kg) if overweight and 25 to 42 lb (11.3 to 19.1 kg) with obesity. For underweight it gives 50 to 62 lb (22.7 to 28.1 kg), a range from a 2003 study by Luke and colleagues rather than the IOM.
What if I'm gaining more or less than the range?
It's common to be outside the range for a while, and it doesn't mean anything is wrong. Mention it at your next check-up so your midwife or doctor can look at the whole picture. Please don't diet or try to lose weight during pregnancy unless your clinician suggests it.
How many extra calories do I need when pregnant?
The CDC says most people need no extra calories in the first trimester, about 340 extra a day in the second trimester and about 450 extra a day in the third, for one baby at a healthy weight before pregnancy. Your needs may differ, especially with twins.
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