Pregnancy Weight Gain Calculator

See a general total pregnancy weight-gain range by pre-pregnancy BMI for one baby or twins, plus a week-by-week reference range and progress check for one baby.

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Check your inputs—Complete valid inputs to calculate a current result.

Weight unit

Pre-pregnancy weight

selected weight unit

1 – 1500 selected weight unit

Current weight

selected weight unit

1 – 1500 selected weight unit

Height unit

Height

selected height unit

1 – 300 selected height unit

Pregnancy

Current week of pregnancy

weeks

Completed weeks since the first day of the last menstrual period.

General total pregnancy weight-gain range

11.3–15.9 kg

Change from pre-pregnancy weight7.0 kg
Pre-pregnancy BMI22.0
Approximate end-of-pregnancy weight range71.3–75.9 kg
General reference range for week 203.0–5.2 kg
Where your gain so far sitsAbove the general reference range

General week-by-week reference range, Normal weight (BMI 18.5–24.9), one baby (kg)
Week	Cumulative gain (kg)	Weight (kg)
4	0.2–0.6	60.2–60.6
8	0.3–1.2	60.3–61.2
12	0.5–1.8	60.5–61.8
14	0.9–2.4	60.9–62.4
16	1.6–3.4	61.6–63.4
18	2.3–4.3	62.3–64.3
20	3.0–5.2	63.0–65.2
22	3.8–6.1	63.8–66.1
24	4.5–7.0	64.5–67.0
26	5.2–7.9	65.2–67.9
28	5.9–8.8	65.9–68.8
30	6.7–9.7	66.7–69.7
32	7.4–10.6	67.4–70.6
34	8.1–11.5	68.1–71.5
36	8.8–12.4	68.8–72.4
38	9.6–13.3	69.6–73.3
40	10.3–14.2	70.3–74.2

The weekly range is general reference information derived from the IOM 2009 guidelines, not a diagnosis or a personal target: weight often changes unevenly from week to week, and the first-trimester range is prorated evenly as a simplification. Being outside the range does not by itself mean something is wrong. Discuss your individual goal with your prenatal clinician, especially with BMI ≥40 or a medical condition, and do not restrict food intake on your own.

How this was calculated

Pre-pregnancy BMI = weight (kg) ÷ height (m)²Put in your numbers: 60.00 ÷ 1.650²Answer: 22.0 kg/m² → Normal weight (BMI 18.5–24.9)
Total-gain range for one baby in this BMI group (lb)Put in your numbers: 25–35 lb × 0.45359237Answer: 11.3–15.9 kg
After week 13: range = 1.1–4.4 lb + weekly rate × (week − 13)Put in your numbers: 1.1 + 0.8 × (20 − 13) to 4.4 + 1 × (20 − 13)Answer: 3.0–5.2 kg
Gain so far = current weight − pre-pregnancy weightPut in your numbers: 67 − 60 kgAnswer: 7.0 kg → above the week 20 range

Formula and method

Calculate pre-pregnancy BMI using kg/m², then select the CDC range for the BMI group and pregnancy type. The current weight is used only to display weight change.

Worked example

A pre-pregnancy weight of 60 kg and height of 165 cm give BMI 22.0. For one baby, the total-gain reference range is 25–35 lb, about 11.3–15.9 kg.

Week-by-week reference range

For one baby, the Institute of Medicine 2009 guidelines, as tabulated by ACOG, assume a gain of 1.1–4.4 lb (about 0.5–2 kg) over the first trimester, then a weekly rate in the second and third trimesters that depends on pre-pregnancy BMI. The calculator spreads the first-trimester amount evenly over weeks 0–13, then adds the weekly rate range for each week after week 13.

Worked example: with BMI 22.0 (normal weight) at week 20, the range is 1.1 + 0.8 × 7 = 6.7 lb to 4.4 + 1 × 7 = 11.4 lb, about 3.0–5.2 kg. A gain of 7 kg from 60 kg to 67 kg is above that general range. That is a point to discuss at a prenatal visit, not a diagnosis.

Second- and third-trimester weekly gain rates by pre-pregnancy BMI (IOM 2009, one baby)
Pre-pregnancy BMI	Total gain	Weekly rate, mean (range)
Below 18.5	28–40 lb	1 lb (1–1.3 lb)
18.5–24.9	25–35 lb	1 lb (0.8–1 lb)
25–29.9	15–25 lb	0.6 lb (0.5–0.7 lb)
30 or more	11–20 lb	0.5 lb (0.4–0.6 lb)

Who this applies to, and its limits

The weekly schedule is for singleton pregnancies. For twins, IOM 2009 gives provisional total ranges for normal-weight, overweight and obese pre-pregnancy BMI; it gives no twin guideline for underweight, so that range (50–62 lb) comes from Luke et al. (2003), as tabulated by CDC. Neither gives weekly rates for twins, so the calculator shows only the total for twins, and it does not cover triplets or more. Pre-pregnancy BMI categories are the same for all adults and do not account for body composition, adolescence or medical conditions.

Weight often changes unevenly: nausea early on, fluid shifts and measurement timing all affect a single reading. Being above or below the general range does not by itself mean anything is wrong, and it is not a reason to restrict eating. Your prenatal clinician can set an individual goal.

Frequently asked questions

Is this a weekly target?

No. For one baby it shows a general reference range for the week you enter, derived from the IOM 2009 total and weekly-rate guidelines, alongside the total pregnancy range. It is not a personal target or a diagnosis. Individual progress and goals should be discussed with a prenatal clinician rather than inferred from a single weight.

References

CDC — Weight Gain During Pregnancy — CDC
ACOG Committee Opinion 548: Weight Gain During Pregnancy (Table 1, Institute of Medicine recommendations) — American College of Obstetricians and Gynecologists (2013)

Last updated September 26, 2026. Results are estimates for informational purposes only.