Pregnancy Weight Gain Calculator
With height 65 in, weight before pregnancy 145 lb, weight now 158 lb, weeks pregnant 24 weeks, pregnancy weight gain comes to 157.7 lb — middle of the recommended range now. It is reached in 12 steps, the last of which is (154.9 + 160.4) / 2, and each one is printed on the page with its numbers filled in. The formula is the one published by Institute of Medicine, not an approximation fitted to it.
Where your weight should be at this point in pregnancy, from the 2009 Institute of Medicine ranges for your pre-pregnancy BMI.
Formula and sources checked · How we check
Height 65 in, Weight before pregnancy 145 lb, Weight now 158 lb, Weeks pregnant 24 weeks
157.7 lb
Middle of the recommended range now for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Pre-pregnancy BMI
145 * 703 / (65 * 65)24.127- Recommended total gain, low end
(25)25 lb- Recommended total gain, high end
(35)35 lb- Weekly gain from week 14, low end
(0.8)0.8 lb- Weekly gain from week 14, high end
(1)1 lb- Where your weight should be, low end
145 + (1.1 + 0.8 * 11)154.9 lb- Where your weight should be, high end
145 + (4.4 + 1 * 11)160.4 lb- Middle of the recommended range
(154.9 + 160.4) / 2157.65 lb- Gained so far
158 - 14513 lb- Distance from the range
(0)0 lb- Left to gain by 40 weeks, low end
145 + 25 - 15812 lb- Left to gain by 40 weeks, high end
145 + 35 - 15822 lb
Ask about this in the chatCompare: starting bmi changes the whole range
Worked example
145 lb at 5 ft 5 in is a pre-pregnancy BMI of 24.1 — the healthy-weight band, so 25 to 35 lb over the whole pregnancy. At 24 weeks the range runs 154.9 to 160.4 lb, and 158 lb sits inside it with 12 to 22 lb still to gain.
How to work it out yourself
- 1.The category is set by your BMI before pregnancy, not by your weight now. Someone who started at a BMI of 24 and someone who started at 31 are given different ranges on purpose, and using today’s weight puts you in the wrong one.
- 2.Expect almost nothing in the first trimester — the guideline total is 1.1 to 4.4 lb for the whole thirteen weeks, and morning sickness makes a small loss common and usually harmless.
- 3.From week 14 the rate is what matters more than the total. A steady 0.8 to 1 lb a week at a healthy starting BMI lands inside the range without any arithmetic.
- 4.One reading off the range is not a problem. A trend is worth mentioning at the next appointment, and it is the reason the ranges exist rather than single targets.
Where the range sits, week by week
| Weeks pregnant (weeks) | Middle of the recommended range now | Where your weight should be, low end | Where your weight should be, high end |
|---|---|---|---|
| 8 | 146.7 lb | 145.68 lb | 147.71 lb |
| 12 | 147.5 lb | 146.02 lb | 149.06 lb |
| 16 | 150.5 lb | 148.5 lb | 152.4 lb |
| 20 | 154.1 lb | 151.7 lb | 156.4 lb |
| 24 | 157.7 lb | 154.9 lb | 160.4 lb |
| 28 | 161.3 lb | 158.1 lb | 164.4 lb |
| 32 | 164.9 lb | 161.3 lb | 168.4 lb |
| 36 | 168.5 lb | 164.5 lb | 172.4 lb |
| 40 | 172.1 lb | 167.7 lb | 176.4 lb |
For a 145 lb start at 5 ft 5 in — a BMI of 24.1, the healthy-weight band.
The formula
- Pre-pregnancy BMI
145 * 703 / (65 * 65) - Recommended total gain, low end
(25) - Recommended total gain, high end
(35) - Weekly gain from week 14, low end
(0.8) - Weekly gain from week 14, high end
(1) - Where your weight should be, low end
145 + (1.1 + 0.8 * 11) - Where your weight should be, high end
145 + (4.4 + 1 * 11) - Middle of the recommended range
(154.9 + 160.4) / 2 - Gained so far
158 - 145 - Distance from the range
(0) - Left to gain by 40 weeks, low end
145 + 25 - 158 - Left to gain by 40 weeks, high end
145 + 35 - 158
Source: Institute of Medicine — Weight Gain During Pregnancy: Reexamining the Guidelines (2009), ACOG — Weight gain during pregnancy (Committee Opinion 548), CDC — Weight gain during pregnancy
Questions people actually ask
- How much weight should I gain during pregnancy?
- By pre-pregnancy BMI, from the 2009 IOM guidelines: 28-40 lb if you were underweight, 25-35 lb at a healthy weight, 15-25 lb if overweight, and 11-20 lb with a BMI of 30 or more. Twins raise every band — 37-54 lb at a healthy starting weight.
- I have gained nothing in the first trimester. Is that a problem?
- Usually not. The guideline for the entire first trimester is 1.1 to 4.4 lb, and nausea often makes it a small loss instead. The rate that matters starts at about week 14, and clinicians look at the trend from there.
- What happens if I gain more than the range?
- Gaining above the range raises the chance of a large baby, a caesarean and weight retained after birth; gaining below it raises the chance of a small-for-gestational-age baby and preterm birth. Both are shifts in probability, not verdicts — which is why the guidance is a band several pounds wide.
- Where does the weight actually go?
- At term, roughly 7-8 lb of baby, 1.5 lb placenta, 2 lb amniotic fluid, 2 lb uterus, 2 lb breast tissue, 4 lb extra blood and fluid, and the rest as maternal fat stores that support breastfeeding. Only about a quarter of a healthy 30 lb gain is the baby.
Related
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