Weight Gain Calculator

Estimate a daily calorie target and a rough timeline for gaining weight from your maintenance calories, target weight and chosen calorie surplus.

Body-weight change is dynamic and does not follow a perfectly linear calorie-to-weight rule. Use this result only as a rough planning estimate for adults who are not pregnant or breastfeeding.

Maintained by Live Fitness Check. Last updated: August 13, 2026. How we test our calculators .

About This Calculator

The Weight Gain Calculator helps an adult turn an existing maintenance-calorie estimate into a higher daily intake target by adding a selected calorie surplus. It also shows the amount of weight between the current and goal values and a deliberately rough theoretical timeline.

Methodology

Target calories are calculated as maintenance calories plus the selected daily surplus. The displayed timeline uses a simple static approximation of about 7,700 kcal per kilogram of body-weight change. Real body-weight change is dynamic, so this linear estimate is presented only as a rough comparison rather than a physiological prediction.

Sources

NIDDK — Body Weight Planner: https://www.niddk.nih.gov/health-information/weight-management/body-weight-planner
NIDDK — Research behind the dynamic Body Weight Planner model: https://www.niddk.nih.gov/research-funding/at-niddk/labs-branches/laboratory-biological-modeling/integrative-physiology-section/research/body-weight-planner

Disclaimer

This tool is for adults 18 and older and is not intended for pregnancy, breastfeeding, children or treatment of underweight, eating disorders or medical conditions. The timeline is a rough static estimate; real weight change adapts over time and may differ substantially.

Frequently Asked Questions

What are weight-gain calories?

They are a daily calorie target above estimated maintenance intake. This calculator adds your selected surplus to maintenance calories.

Is the estimated timeline exact?

No. Human body weight responds dynamically to changes in intake and activity, so the timeline is intentionally labeled as a rough linear estimate.

Where do I get maintenance calories?

You can estimate them with the separate Maintenance Calorie Calculator and then use that result here as a starting point.

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