Free BMR Calculator — Why You Gain Weight Every Year

Last updated: April 17, 2026

MoneyMath's BMR calculator estimates resting calorie burn and shows how age, muscle loss, and unchanged eating habits can create gradual weight gain over time.

Free to useRuns in your browserTransparent assumptions

Free BMR calculator showing age-related decline and creeping weight gain. See your BMR timeline from 25 to 75, cumulative weight gain if you don't adjust, and how strength training slows the decline.

Use the BMR Calculator to compare realistic scenarios before making a money, health, or planning decision.

Adjust the inputs and review the result breakdown so you can see which assumptions matter most.

How to use this calculator

Step 1Enter your starting information. Add the core inputs requested by the BMR Calculator, such as amounts, dates, rates, income, weight, or other scenario details.
Step 2Review the calculated result. Read the headline answer first, then scan the supporting breakdown, chart, or comparison table.
Step 3Compare another scenario. Change one input at a time to understand what drives the result and which option is most realistic.

Formula, Sources & Assumptions

Formula

BMR uses standard sex-specific BMR equations, then compares the result with age-related metabolism scenarios.

Assumptions

Results are estimates for planning and education.
Actual costs, taxes, rates, or outcomes may differ based on personal circumstances and updated rules.