Starting BMI changes the whole range
145 lb gives 157.7 lb. 185 lb gives 193.3 lb — a difference of 35.6 lb more (+22.6%).
The same height and week, two starting weights: 185 lb at 5 ft 5 in is a BMI of 30.8, which moves the recommendation to 11-20 lb for the whole pregnancy.
| Input | 145 lb | 185 lb |
|---|---|---|
| Height(in) | 65 | 65 |
| Weight before pregnancy(lb) | 145 | 185 |
| Weight now(lb) | 158 | 158 |
| Weeks pregnant(weeks) | 24 | 24 |
| Carrying | One baby | One baby |
| Middle of the recommended range now | 157.7 lb | 193.3 lb |
Every figure, both ways
| Step | 145 lb | 185 lb | Difference |
|---|---|---|---|
| Pre-pregnancy BMI | 24.13 | 30.78 | +6.66 |
| Recommended total gain, low end(lb) | 25 | 11 | -14 |
| Recommended total gain, high end(lb) | 35 | 20 | -15 |
| Weekly gain from week 14, low end(lb) | 0.8 | 0.4 | -0.4 |
| Weekly gain from week 14, high end(lb) | 1 | 0.6 | -0.4 |
| Where your weight should be, low end(lb) | 154.9 | 190.5 | +35.6 |
| Where your weight should be, high end(lb) | 160.4 | 196 | +35.6 |
| Middle of the recommended range(lb) | 157.65 | 193.25 | +35.6 |
| Gained so far(lb) | 13 | -27 | -40 |
| Distance from the range(lb) | 0 | -32.5 | -32.5 |
| Left to gain by 40 weeks, low end(lb) | 12 | 38 | +26 |
| Left to gain by 40 weeks, high end(lb) | 22 | 47 | +25 |
Questions people actually ask
- Does raising weight before pregnancy change the answer in proportion?
- No, and that is the point of putting them side by side. Weight before pregnancy changes by 28% while middle of the recommended range now changes by 23%. The step table below shows which line breaks the proportion.
- What is held constant between the two columns?
- Everything except weight before pregnancy: height, weight now, weeks pregnant, carrying. That is what makes the difference attributable — change two things at once and neither column tells you which one moved the answer.
- Can I compare my own two numbers?
- Yes, from the address bar: add ?a.pre_weight=… and &b.pre_weight=… to set each side, and a parameter without a prefix sets both at once. The page is computed per request, so any pair works — these two are only the ones worth a link.
Change either side by adding query parameters — ?a.pre_weight=… and b.pre_weight=…. A parameter without a prefix sets both sides at once. 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