Calorie Deficit / Surplus Calculator
TDEE-based targets for losing, maintaining or gaining weight, at three weekly-rate tiers
How the target is calculated
This calculator starts from the same TDEE engine as the TDEE calculator (basal metabolic rate × activity factor), then applies a weight-proportional daily adjustment instead of a flat percentage:
Daily target = TDEE ± (bodyweight × weekly rate% × 7,700 kcal/kg ÷ 7)
The weekly rate is expressed as a percentage of your bodyweight rather than a fixed number of kilograms, so the deficit or surplus scales with your size. Three tiers are shown side by side rather than a single aggressive number: mild (~0.25% of bodyweight/week), moderate (~0.5%/week) and aggressive (~0.75%/week). Choosing maintain as the goal returns your TDEE unchanged at all three tiers.
Which rate tier to choose
| Tier | Rate | Typical use |
|---|---|---|
| Mild | ~0.25% of bodyweight/week | Slow, easier to sustain; preferred when little weight needs to change |
| Moderate | ~0.5% of bodyweight/week | Common general-purpose starting point |
| Aggressive | ~0.75% of bodyweight/week | Faster change; harder to sustain and more likely to affect muscle mass or energy levels — use with more caution, ideally with guidance |
Faster is not automatically better: very large deficits are harder to sustain, can affect muscle mass and energy levels, and tend to be followed by regain. The mild or moderate tier is a reasonable default for most goals.
How to interpret the result
The calculator shows your basal metabolic rate, your TDEE (maintenance calories) and a target for each rate tier, together with the bodyweight change per week that target implies. Use the target as a starting point and adjust it every few weeks based on your actual weight trend, since individual energy needs vary.
What to do with your result
This is the natural next step after calculating your TDEE — the same basal metabolic rate, from Mifflin-St Jeor or Harris-Benedict, feeds both tools. Once you have a calorie target, the macronutrient split tool turns it into protein, carbohydrate and fat grams.
When to see a professional: for a large amount of weight to lose or gain, an eating disorder history, pregnancy, or any medical condition, work with a doctor or dietitian rather than following a calculator alone.
Limitations
- The 7,700 kcal/kg rule (from Wishnofsky's 1958 estimate) is a useful approximation, not a fixed physical law: energy expenditure adapts as weight changes, so real-world results are usually somewhat slower than a straight-line calculation predicts, especially over many weeks.
- It assumes the deficit or surplus is maintained consistently; day-to-day intake naturally varies.
- It does not account for changes in body composition (muscle vs fat) or individual metabolic adaptation.
- This is an informational estimate, not a dietary prescription.