Calorie Calculator for Weight Loss

Losing weight requires eating less energy than you spend. Everything else — which foods, which schedule, which app — is a strategy for making that gap livable. The calculator estimates your expenditure and highlights the weight-loss line, set 20% below it. Enter metric values: 180 lb is 81.6 kg, 5 ft 9 in is 175 cm.

Size the deficit as a percentage, not as a flat number

The advice you have heard is “cut 500 calories a day.” It is not wrong so much as unit-blind. Look at what that same subtraction means to different people:

Daily expenditure	Cut 500 kcal	That is a deficit of
1,800 kcal	1,300 kcal	28%
2,200 kcal	1,700 kcal	23%
2,600 kcal	2,100 kcal	19%
3,000 kcal	2,500 kcal	17%

A small, lightly active person handed the standard advice is cutting nearly a third of her intake. A large, active person is barely noticing. Expressing the deficit as a share of expenditure keeps the difficulty roughly constant, which is why the calculator uses a percentage. Fifteen to twenty percent is a workable starting band for most people; the arithmetic that converts either version into pounds per week lives on the calorie deficit calculator.

Aim for a percentage of your body, too

Weight-loss goals tend to be round and arbitrary — 30 lb, or a number from high school. The NIDDK frames the first target differently: losing 5% of your body weight over about six months is a reasonable initial goal. That is 10 lb for a 200 lb starting point, and the how many calories to lose 10 pounds page walks through exactly what that costs and how long it takes.

Five percent sounds modest next to a transformation photo. It is also achievable, keeps the deficit shallow enough to sustain, and can be repeated.

What protects muscle while the fat goes

A deficit takes tissue from wherever the body finds it easiest. Two things bias that choice toward fat:

• Protein. The 2016 joint position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine puts daily protein at 1.2 to 2.0 g per kg of body weight, and notes that higher intakes within that range are indicated when energy intake is being reduced. For a 180 lb (81.6 kg) person that is roughly 98 to 163 g a day.
• Resistance training. Nothing else tells the body the muscle is still needed.

Skip both and a large share of the weight you lose is lean mass — which lowers your expenditure and makes the next round harder.

When the deficit stops working

It rarely stops. What happens is that the deficit shrinks without you changing anything: you are lighter, so your maintenance is lower, so yesterday’s calorie target is closer to today’s break-even. Recalculate every 10 lb or so, and check your maintenance figure against the maintenance calorie calculator before assuming your metabolism has broken.

This content is informational and does not replace advice from a physician or registered dietitian. If you have a history of disordered eating, work through calorie targets with a clinician rather than alone.