Resting Metabolic Rate (Cunningham) Calculator

How it is calculated

The tool first strips out fat: LBM = weight × (1 − body fat % ÷ 100), with weight in kilograms and body fat as a percentage. Resting metabolic rate then follows the Cunningham line: RMR = 500 + 22 × LBM, in kcal per day. Two ready-made daily totals are shown by multiplying RMR by a fixed activity factor: × 1.2 for a sedentary day and × 1.55 for an active one. Results are rounded to whole kcal, and lean mass to two decimals. Weight must be above zero and body fat must be 0 or more but below 100, otherwise no result appears. The equation uses only lean mass, so age and sex do not matter, and the answer is only as good as the body fat figure you enter. It estimates energy at rest; real needs also depend on training and daily movement.

Common mistakes

• Entering body fat as a decimal (0.15) instead of a percentage (15). The tool accepts it, sees almost 100% lean mass and gives 2,257 kcal/day instead of 1,996, overstating RMR by hundreds of kcal.
• Using the sedentary or active totals as a fat-loss target without subtracting a deficit; they are maintenance-style figures, not a diet.
• Taking a body fat reading from a scale that fluctuates with hydration, since each point of fat moves RMR by about 18 kcal at this weight.
• Typing weight in pounds into the kilogram field. 176 lb entered as 176 gives an RMR of 3,791 kcal/day, far above the real figure.
• Using the Cunningham result for someone with no reliable body fat measurement; the whole benefit of the formula depends on that input.