Pregnancy Weight Gain Calculator — Week-by-Week Targets

This tool uses pre-pregnancy BMI to show typical ranges for total weight gain and weekly targets in the second and third trimesters. Ranges are intentionally broad so they work with real-world variation. As a quick rule of thumb, the first trimester often adds a small total amount, and steady weekly changes are more common from week 14 onward. The calculator keeps everything in either kilograms and centimeters or pounds and feet/inches—no mixing—so it’s globally understood.

• Enter height and pre-pregnancy weight to see your BMI band.
• Pick your current week to view cumulative targets up to today.
• Optional: enter current weight to compare with the range.

Typical single-baby ranges often used in public resources:

• Underweight (BMI < 18.5): total ~12.5–18 kg (28–40 lb); weekly in 2nd/3rd trimester ~0.44–0.58 kg (1.0–1.3 lb).
• Normal (18.5–24.9): total ~11.5–16 kg (25–35 lb); weekly ~0.35–0.50 kg (0.8–1.0 lb).
• Overweight (25–29.9): total ~7–11.5 kg (15–25 lb); weekly ~0.23–0.33 kg (0.5–0.7 lb).
• Obesity (≥ 30): total ~5–9 kg (11–20 lb); weekly ~0.17–0.27 kg (0.4–0.6 lb).

First trimester (weeks 1–13): many sources suggest a small total gain around 0.5–2.0 kg (1–4.5 lb). The planner spreads this gently across the first 13 weeks, then applies your weekly range from week 14 to term. Your clinician may personalize these numbers based on your health, history, appetite, nausea, and activity level.

Tips for using the plan: focus on patterns across weeks rather than any single day. If morning sickness or illness changes weight early on, discuss it with your care team; the plan is flexible and can be adjusted later. If you track weight, try a consistent routine—similar time of day, similar clothing—and look at a rolling average. Combine this with other signposts of a healthy pregnancy such as energy, sleep, movement, and routine check-ups.

Limits and care: this page is educational. It does not diagnose or replace prenatal care. Twin or higher-order pregnancies, medical conditions, and special dietary needs require individualized guidance. If you notice rapid changes, dizziness, severe swelling, or other concerning symptoms, contact your clinician or local emergency services.

The Pregnancy Weight Gain Calculator classifies pre-pregnancy BMI from your height and starting weight. It assigns a first-trimester total range and a weekly range for weeks 14–40. It then calculates a cumulative target range for each week by adding a gentle first-trimester slope and a steady second/third-trimester slope. If you add your current weight, the tool compares your actual change with the cumulative range and shows a simple status badge.