Use this free calorie deficit calculator to estimate your maintenance calories, choose a practical target for weight loss and, if you know your body-fat percentage, compare it with the popular 22-calorie rule.
A calorie deficit is the gap between the calories your body uses and the calories you consume. Creating a manageable deficit is the basis of fat loss, but the right amount is individual: it depends on your body size, activity, starting body-fat level and how well you need to maintain training performance and recovery.
Use this free calorie deficit calculator to estimate your maintenance calories, choose a practical target for weight loss and, if you know your body-fat percentage, compare it with the popular 22-calorie rule. Treat the result as a sensible starting point, then adjust it according to your real progress over the following few weeks.
How to work out your calorie deficit
A calorie deficit means consuming less energy than you use. This calculator first estimates your basal metabolic rate using the Mifflin-St Jeor equation, then applies an activity multiplier to estimate your maintenance calories, often called TDEE.
It then shows three possible daily targets: a gentle 15% deficit, a moderate 20% deficit and a more aggressive 25% deficit. These are starting estimates, not prescriptions. Track your average body weight, waist measurement, gym performance, hunger and recovery for two to three weeks, then adjust if needed.
What is a good calorie deficit for weight loss?
For many people, a moderate calorie deficit is the most sustainable place to start. The right figure depends on body size, activity, training goals and how lean you already are. Rather than chasing the largest possible number, choose a deficit that still lets you train well, eat enough protein and stick to the plan.
People who are already lean, resistance trained or dieting for a long period normally have a stronger reason to lose weight at the more conservative end of the range. A commonly used guide for people prioritising muscle retention is around 0.5% to 1% of body weight per week, with the lower end generally more appropriate as you get leaner.
The 22-calorie rule: an optional upper guardrail
If you enter an estimated body-fat percentage, the calculator also multiplies your pounds of fat mass by 22. This is the popular “22-calorie rule” sometimes used to estimate a theoretical upper limit for a deficit while preserving muscle.
It is useful as a sense-check, especially because it illustrates why a very lean person may not tolerate the same deficit as someone carrying much more body fat. It is not a precise, scientifically proven line below which no muscle can be lost. The original 2005 paper behind the idea published a higher theoretical value of about 31 calories per pound of body fat; the 22-calorie version is attributed to a later, unpublished revision.
Read our full evidence review: What Is the Maximum Calorie Deficit Without Losing Muscle? The 22-Calorie Rule Examined.
How to lose fat without losing muscle
No calculator can guarantee that every kilogram lost is fat. Muscle retention is influenced by the size and duration of the deficit, starting body fat, resistance training, protein intake, sleep, recovery and the accuracy of your food tracking.
Keep resistance training in your routine and aim to preserve performance where possible. Protein needs can be higher during dieting; lean, resistance-trained athletes may benefit from roughly 2.3 to 3.1g of protein per kilogram of fat-free mass per day. For most active people, consistently meeting a high daily protein intake is more important than chasing perfect meal timing.
Frequently asked questions
How big should my calorie deficit be?
Start with a gentle to moderate deficit, then judge it by your actual progress. If weight is falling too quickly, performance is declining or recovery is poor, the deficit may be too large.
Is a 500-calorie deficit right for everyone?
No. It can be a reasonable starting point for some people, but it may be aggressive for a small or already-lean person and modest for a larger person. A percentage-based target is often a more useful first estimate.
How accurate is this calorie deficit calculator?
It is an estimate. Activity multipliers, food labels, body-fat measurements and wearable calorie estimates all have error. Use the result as a starting point and refine it from several weeks of real-world data.
Can I use this calculator if I exercise?
Yes. Select the activity level that best reflects your average week, not an unusually busy day. Do not automatically add every calorie shown by a watch on top of this estimate.
