Calorie Deficit Calculator
Calculate your ideal calorie deficit for safe, sustainable weight loss. Free calculator with personalized daily targets, timeline, and macro breakdown.
Calorie Deficit at a glance
Rather than a generic target, the Calorie Deficit below is built from your own energy needs - the deficit you choose comes off your maintenance figure, and the timeline reflects a rate you can actually keep.
Calculate your ideal calorie deficit for safe, sustainable weight loss. Free calculator with personalized daily targets, timeline, and macro breakdown.
The page is written for people cutting on purpose: the deficit slots into the same diary tools Macrition uses, so every logged day shows whether you landed inside the deficit you planned.
The science of the calorie deficit
Weight loss is governed by thermodynamics. To lose fat, you must consume fewer calories than your body expends, creating a calorie deficit. One pound of body fat contains approximately 3,500 calories of usable energy, so a daily deficit of 500 calories produces a one-pound weekly loss.
Why aggressive deficits backfire
Deficits exceeding 1,000 calories per day typically trigger adaptive thermogenesis: your metabolism slows, hunger hormones spike, lean muscle is catabolized for energy, and the eventual rebound is often worse than the starting point. A moderate deficit of 500-750 calories is the sweet spot.
Preserving muscle during a cut
To bias the breakdown toward fat and spare muscle: maintain adequate protein intake (1.6-2.2 g per kg of body weight) and continue resistance training.
Formula sources, population limits, and references for this macronutrient calculator are documented in our public methodology. Read the methodology · Medical disclaimer