Calorie Deficit Calculator
This calorie deficit calculator estimates a daily calorie target by combining your BMR, activity level, and chosen deficit percentage. Enter your sex, age, weight, height, average activity factor, and target deficit to see your estimated BMR, estimated maintenance calories, and the calorie intake that sits below maintenance by the percentage you selected. A calorie deficit means eating fewer calories than your body uses over time. Many adults start with a modest deficit because it is easier to follow, easier to recover from, and easier to adjust if progress is slower or faster than expected. This page is most useful for planning a starting target, comparing small versus aggressive deficits, and understanding how maintenance calories and deficit size interact before you build meals around the result. The estimate is only a starting point. Real calorie needs change with body size, routine, training volume, stress, sleep, medications, and how closely an activity factor matches your actual week.
Quick answer
The calculator uses the Mifflin-St Jeor equation to estimate BMR from sex, age, weight, and height.
Estimate only. This tool does not provide personal medical advice.
What this tells you
- •The calculator uses the Mifflin-St Jeor equation to estimate BMR from sex, age, weight, and height.
- •It multiplies BMR by your activity factor to estimate TDEE, which is your approximate maintenance intake before any planned deficit.
- •Your chosen deficit percentage is applied to estimated TDEE, not to BMR, so the target reflects total daily energy use rather than resting needs alone.
- •A 10% deficit is smaller and often easier to sustain, while a 20% deficit removes more calories each day and may feel harder during training or busy weeks.
- •The result works best as a starting estimate that you compare against weight trends, hunger, recovery, and adherence over the next few weeks.
How to Use
- 11. Enter your sex, age, body weight in kilograms, and height in centimeters using current values instead of old stats from a past diet phase.
- 22. Choose the activity factor that matches your average week, not your best workout day. If you have a desk job but train three times per week, the lightly active or moderately active options are often more realistic than the highest setting.
- 33. Pick a deficit percentage. Many people begin around 10% to 20% because the intake drop is easier to live with than a very aggressive cut.
- 44. Calculate and review all four outputs together. BMR shows resting needs, TDEE shows estimated maintenance, target calories show the planned intake, and calorie deficit shows the estimated daily gap from maintenance.
- 55. Use the result to shape meals, then monitor trend weight, gym performance, hunger, and energy for two to three weeks. If progress is far from expected, adjust the activity factor or deficit rather than assuming the first estimate must be exact.
How It Works
Formula
BMR (male) = 10W + 6.25H - 5A + 5
BMR (female) = 10W + 6.25H - 5A - 161
TDEE = BMR × activity factor
Target Calories = TDEE × (1 - deficit% ÷ 100)The formula starts with BMR, or basal metabolic rate, which estimates how many calories your body would use at rest. In these equations, W is weight in kilograms, H is height in centimeters, and A is age in years. After BMR is estimated, the calculator multiplies it by your selected activity factor to estimate TDEE, or total daily energy expenditure. That value is your rough maintenance intake. The deficit step is percentage based. If TDEE is 2,500 calories and you choose a 20% deficit, the tool removes 20% of 2,500, which is 500 calories, and returns a target of 2,000 calories. The code rounds each displayed output to the nearest whole calorie. This keeps the result readable while staying faithful to the underlying calculation.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Moderately active male with a 20% deficit
BMR = 10 × 80 + 6.25 × 180 - 5 × 30 + 5 = 1780. TDEE = 1780 × 1.55 = 2759. A 20% deficit gives 2759 × 0.80 = 2207.2, which the tool displays as 2207 calories. The gap between maintenance and target is 551.8 calories, displayed as 552.
Lightly active female with a 15% deficit
BMR = 10 × 68 + 6.25 × 165 - 5 × 34 - 161 = 1380.25, which displays as 1380. TDEE = 1380.25 × 1.375 = 1897.84375, displayed as 1898. Applying a 15% deficit gives 1897.84375 × 0.85 = 1613.1671875, so the target displays as 1613 calories. The displayed deficit rounds to 285 calories per day.
Sedentary male using a gentle 10% deficit
BMR = 10 × 95 + 6.25 × 178 - 5 × 42 + 5 = 1857.5, which rounds to 1858. TDEE = 1857.5 × 1.2 = 2229. A 10% deficit uses 2229 × 0.90 = 2006.1, so the displayed target is 2006 calories. This example shows how a smaller percentage can still create a meaningful daily gap without pushing intake as low as a harder cut.
Moderately active female planning a 20% cut
BMR = 10 × 59 + 6.25 × 162 - 5 × 29 - 161 = 1296.5, displayed as 1296. TDEE = 1296.5 × 1.55 = 2009.575, displayed as 2010. With a 20% deficit, target calories are 2009.575 × 0.80 = 1607.66, which rounds to 1608. The displayed daily deficit rounds to 402 calories.
Very active male choosing an 18% deficit
BMR = 10 × 72 + 6.25 × 175 - 5 × 26 + 5 = 1688.75, which rounds to 1689. TDEE = 1688.75 × 1.725 = 2913.09375, displayed as 2913. Applying an 18% deficit gives 2913.09375 × 0.82 = 2388.736875, displayed as 2389 calories. The resulting daily gap displays as 524 calories, which is a reminder that the same percent can remove a larger calorie amount for a more active person.
Common calorie deficit ranges
Percent deficits remove a share of estimated TDEE, so the calorie gap grows as maintenance calories rise.
| Deficit | How it is often used | Planning note |
|---|---|---|
| 5% to 10% | Small adjustment or slow cut | Often easier to recover from and easier to pair with hard training |
| 10% to 15% | Moderate starting range | Common when someone wants steady progress without a sharp intake drop |
| 15% to 20% | Firmer short-term cut | Useful when adherence is solid and recovery, hunger, and performance stay acceptable |
| 20% to 25% | Aggressive range | Needs closer monitoring because energy, recovery, and diet adherence may suffer |
| Above 25% | Special cases only | Often harder to sustain and better reviewed with a qualified clinician or dietitian |
The calculator allows up to 40%, but a higher limit in code does not mean the same level is appropriate for most people.
Why the same deficit percent gives different calorie targets
A calorie deficit percent is relative, not fixed. Ten percent of a 1,900 calorie TDEE is 190 calories. Ten percent of a 2,900 calorie TDEE is 290 calories. That is why two people can choose the same deficit percent and still receive targets that differ by several hundred calories per day.
This is also why a flat rule such as 500 calories per day does not fit every situation equally well. For one person, 500 calories may be close to a moderate 15% to 20% cut. For another person with lower maintenance needs, the same 500-calorie drop may be much more aggressive. A percentage method helps scale the target to body size and activity level.
Targets also change over time. If body weight falls, training volume changes, or daily movement drops during a diet, true maintenance calories can move lower. Rechecking the estimate after a meaningful weight change can keep the plan closer to reality and reduce the chance of sticking to an outdated target.
The best use of this page is to set a reasonable starting point, then compare it with real-world feedback. If the target looks fine on paper but leaves you exhausted, hungry, or unable to train well, the plan may be too aggressive even if the math itself is correct.
Common mistakes
- Picking the highest activity factor because of one or two hard workouts instead of matching the average full week.
- Using goal weight instead of current weight, which makes the starting estimate less accurate.
- Treating the first result as exact and never adjusting after new body-weight trend data comes in.
- Choosing an aggressive deficit even when hunger, recovery, sleep, or training quality already feel strained.
- Comparing your target to someone else's plan without accounting for different body size, activity, and maintenance calories.
- Forgetting that calorie targets are only one part of the picture and still need food quality, protein, fiber, and consistency.
Limitations
This calculator is an estimate model based on the Mifflin-St Jeor BMR equation and a broad activity-factor system. It assumes your current body weight, height, age, and selected activity level give a useful starting picture of maintenance calories, but it cannot measure your actual daily energy expenditure directly. It does not account for body-composition differences, unusually high or low non-exercise movement, metabolic adaptation during long diet phases, menstrual-cycle changes, medical conditions, medications, or the behavioral side of dieting. Use the result as a planning estimate, then compare it with trend weight, performance, appetite, and recovery before making larger changes.
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