Caloric Deficit Calculator
Give this your maintenance calories and the weight you are aiming for, and it returns the intake that gets you there, how fast the weight moves, and the day you arrive. It answers that last question twice: once with the familiar 3,500 calories per pound rule, and once with maintenance allowed to fall as you do. The two answers are weeks or months apart, and the second is the one worth planning around.
- Accurate
- Real-time
- Easy to use
- 100% free
Daily calorie target
2,059 kcal/day
Weight to lose
10.0 kg
Details
Updates as you typeUsed only for the minimum intake considered safe without medical supervision.
The calories you burn in an average day. The TDEE calculator estimates this if you do not know it.
A goal above your current weight is fine — the same energy balance runs in reverse.
How fast you want the weight to move. Faster means a bigger deficit, which the safe-intake floor may refuse.
The day you begin. Both projected goal dates are counted from here.
Summary
Moderate deficitDaily calorie target
2,059 kcal/day
Maintenance calories
2,500 kcal/day
- Daily calorie target2,059 kcal/day82%
- Daily deficit441 kcal/day18%
- Daily deficit
- 441 kcal/day
- Weight to lose
- 10.0 kg
- Planned weekly rate
- 0.40 kg/week
- Goal date (3,500 rule)
- 13 February 2027
- Goal date (with adaptation)
- 22 April 2027
- Time to goal (3,500 rule)
- 5 months 25 days
- Time to goal (with adaptation)
- 8 months 3 days
- Average weekly rate to that date
- 0.29 kg/week
- Still to go on the 3,500-rule date
- 2.1 kg
- Plateau at this intake
- 65.0 kg
- The 3,500 kcal per pound figure is Wishnofsky’s 1958 approximation. It assumes the tissue lost is pure fat and that your metabolism never adapts, so it projects a straight line and systematically overpredicts loss the longer it runs.
- The adaptive projection lets maintenance fall as you do, at roughly 10 kcal a day per pound of body weight — the rule of thumb from Hall and colleagues. That gives a 350-day time constant and a plateau, here 65.0 kg, beyond which this intake cannot take you however long you hold it.
- The two methods disagree by 68 days on this plan, and the gap widens with distance: on the date the 3,500 rule promises your goal, the adaptive model still has you 2.1 kg away.
- Neither line is a promise. Both assume perfect adherence and neither models changes in body composition, water weight, or the drop in unconscious daily movement that usually accompanies a deficit. Recalculate every few kilograms.
How this is calculated
- Maintenance calories
- 2,500 kcal/day
- Target rate of change
- 0.40 kg/week
- Energy per unit of body weight
- 7,716 kcal/kg
- Requested gap = rate x energy / 7
- 441 kcal/day
- Safe intake floor
- 1,500 kcal/day
- Deficit applied
- 441 kcal/day
- Daily calorie target = maintenance - deficit
- 2,059 kcal/day
- Weight to lose
- 10.0 kg
- Days (3,500 rule) = change x energy / deficit
- 175.0 days
- Goal date (3,500 rule)
- 2027-02-13
- Maintenance moves by
- 22.0 kcal/day per kg
- Plateau = current + gap / that slope
- 65.0 kg
- Time constant = 3,500 / 10
- 350 days
- Share of the plateau your goal needs
- 50.0%
- Days (adaptive) = -350 x ln(1 - that share)
- 242.6 days
- Goal date (with adaptation)
- 2027-04-22
Days
Compare scenarios
See how one change moves the result
- CurrentYour inputs as they stand2,059 kcal/dayCurrent
- Maintenance calorieskcal/day 3,1502,709 kcal/day
- Goal weightkg 942,941 kcal/day
For informational purposes only. This is not medical advice — consult a healthcare professional about your health.
Frequently asked questions
How big a calorie deficit do I need to lose 1 kg a week?
One kilogram is treated as about 7,716 calories, so a kilogram a week needs a deficit of roughly 1,102 calories a day. For most people that pushes intake below the level considered safe without medical supervision, which is why this calculator caps the deficit and shows the fastest plan that stays above the floor instead.
Why does the 3,500 calories per pound rule not work?
It comes from Max Wishnofsky in 1958 and assumes two things that are not true over months: that everything you lose is fat, and that your metabolism is unchanged by losing it. In reality a smaller body costs less to run, so your maintenance figure falls as your weight does and the same intake becomes a smaller and smaller deficit. The rule is close enough for a fortnight and increasingly wrong after that, always in the optimistic direction.
How does this calculator model metabolic adaptation?
It uses the rule of thumb from Kevin Hall and colleagues that a lasting change of about 10 calories a day in intake corresponds to about one pound of eventual weight change. Read as a slope, that means maintenance falls roughly 10 calories a day for every pound you lose. Combined with the 3,500 figure it gives a 350-day time constant: weight change is about 63% complete after a year and then flattens toward a plateau.
Why does the calculator say my goal is never reached?
Because a fixed intake has a fixed plateau. At the modelled slope, the total weight an intake can ever take off is about 50 times your weekly target rate — so a plan built around losing 0.4 kg a week bottoms out after 20 kg, regardless of how long you hold it. Reaching a goal beyond that means recalculating partway with your new, lower maintenance figure.
Why will the calculator not show me a very low calorie plan?
Intakes below roughly 1,200 calories a day for women and 1,500 for men are very-low-calorie diets, which are clinical interventions run with medical supervision because of the risk to muscle mass, micronutrient intake, and gallbladder health. If your requested rate would breach that floor, the deficit is capped and the page says so rather than printing a plan it should not be handing out.
Do I need my TDEE before using this?
Yes — maintenance calories are the one input this page does not estimate for you, because that is the TDEE calculator’s job. Work it out there from your height, weight, age, sex and activity level, or use two to three weeks of tracked intake at stable weight, which is the more accurate route if you have the data.