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Calorie Deficit Calculator — Daily Target and Timeline

Pick a goal weight and pace. Get your daily calorie target and projected end date.

ft in

1 lb/week ≈ 500 kcal/day deficit. Range: 0.5–2 lb/week (0.25–1 kg/week).

TDEE (maintenance)
—
kcal/day to maintain weight
Daily target
—
—

What is calorie deficit calculator?

A calorie deficit (or surplus) is the difference between what your body burns and what you eat. The math behind every weight-change plan rests on two constants: 1 lb of body weight ≈ 3,500 kcal, and 1 kg ≈ 7,700 kcal. A 500 kcal/day deficit, sustained for a week, predicts about 1 lb of loss; a 250 kcal/day surplus predicts about 0.5 lb of gain.

This calculator chains four steps from physio.ts:

  1. BMR — Mifflin-St Jeor 1990 formula on your stats.
  2. TDEE — BMR multiplied by an activity factor (1.2 sedentary through 1.9 extremely active).
  3. Daily deficit/surplus — your weekly rate × kcal-per-unit ÷ 7.
  4. Daily target — TDEE minus deficit (or plus surplus).

The projected end-date below the result is computed from your current weight, goal weight, and weekly rate — weeks = |delta| ÷ rate. It assumes your TDEE stays constant, which isn’t quite true: TDEE drops as you lose weight (less mass to maintain plus suppressed NEAT), so a long cut typically runs 10–20% behind the original projection. The fix is to recompute the calculator monthly at your current weight; the timeline rebases each time.

Two safety details worth naming. First, the pace clamp: 0.5–2 lb/week (0.25–1 kg/week) is the well-validated sustainable range. Past 2 lb/week, an increasing share of the loss is lean tissue rather than fat — bad for performance, body composition, and regain. The calculator rejects rates outside the range with a hint. Second, the 1,200 kcal/day floor: when the daily target drops below that, a warning panel appears. The clinical guideline is that adult intake below 1,200 (women) or 1,500 (men) calls for registered-dietitian supervision rather than DIY tracking — adaptive thermogenesis becomes severe, micronutrient gaps multiply, and adherence collapses.

Privacy is the final detail worth naming. Every calculation runs locally in your browser. Your inputs are never transmitted. The only state saved is your unit preference (imperial vs. metric) in localStorage, shared across all our fitness tools. Estimates only — not medical advice.

When to use a calorie deficit calculator

  • Starting a cut — Pick a goal weight, pick a pace, and you get a daily calorie target plus a projected end date. The 1 lb/week default works out to a 500 kcal/day deficit (the classic '3500 kcal per pound' rule) — aggressive enough to see weekly progress without crashing into adherence problems.
  • Recalibrating mid-cut as the scale moves — After 5–10 lb of loss your TDEE has dropped 200–300 kcal/day. Re-enter your current weight to recompute the target. The end-date readout shifts too — the new pace assumes the lower TDEE, so the timeline is more honest than the original projection.
  • Bulking on a target rate — Goal weight greater than current weight enables the surplus path. The rate clamps at 0.5–2 lb/week (0.25–1 kg/week) — past 2 lb/week, gains are mostly fat. The default 0.5 lb/week is the lean-bulk pace most strength coaches recommend.

How to use the Calorie Deficit Calculator — Daily Target and Timeline

  1. Enter your stats — Same Mifflin-St Jeor inputs as the BMR/TDEE calculators — units, sex, age, current weight, height, activity level. The TDEE is computed first as your maintenance number.
  2. Set goal weight and weekly rate — Goal weight can be above or below current weight (the calculator handles both deficit and surplus). Weekly rate clamps at 0.5–2 lb/week (0.25–1 kg/week) — outside that range, the projection clears with a hint.
  3. Read your daily target — The headline is the calories per day you'd eat to hit your goal at the chosen pace. The math: 1 lb of body weight ≈ 3,500 kcal, so 1 lb/week ≈ 500 kcal/day deficit; 1 kg ≈ 7,700 kcal.
  4. Check the projected end date — The timeline assumes your TDEE stays constant — in reality TDEE drops as you lose weight, so a long cut will run slightly behind the projection. Recompute monthly with your current weight to keep the timeline honest.
  5. Heed the floor warning — If the daily target drops below 1,200 kcal/day, the warning panel appears. That's the conventional clinical floor for adults, below which most reputable nutrition guidance shifts from 'eat less' to 'work with a registered dietitian.' Slow the pace or accept a longer timeline.

Worked examples

Standard cut: 35y M 180lb 5'10" moderate, goal 170 lb at 1 lb/wk

Input:  Male, 35y, 180 lb, 5'10", Moderate, goal 170, 1 lb/week
Output: TDEE 2,724 → target ≈ 2,224 kcal/day, ~10 weeks

Classic 500 kcal/day deficit. About 2.5 months to drop 10 lb at this rate.

Aggressive cut: 30y F 165lb 5'5" light, goal 145 lb at 1.5 lb/wk

Input:  Female, 30y, 165 lb, 5'5", Light, goal 145, 1.5 lb/week
Output: TDEE ~2,002 → target ≈ 1,252 kcal/day, ~13 weeks

1.5 lb/week is the upper end of sustainable — at this pace the daily target lands close to the 1,200 kcal/day floor, which is why the warning may appear.

Lean bulk: 25y M 150lb 5'10" active, goal 165 lb at 0.5 lb/wk

Input:  Male, 25y, 150 lb, 5'10", Active, goal 165, 0.5 lb/week
Output: TDEE ~2,938 → target ≈ 3,188 kcal/day, ~30 weeks

Surplus path. About 7 months for 15 lb of clean gain — most of the added weight will be lean tissue at this pace.

Frequently asked questions

Where does the 3,500 kcal per pound rule come from?
Body fat is about 3,500 kcal/lb (7,700 kcal/kg) of stored energy when accounting for the small water and protein content of adipose tissue. So a 500 kcal/day deficit, sustained, predicts about 1 lb/week of loss. The rule is a useful approximation but not a law — at long durations adaptive thermogenesis (lower NEAT, mild thyroid suppression) means the actual loss runs about 70–80% of the predicted rate. The end-date readout is a planning tool, not a prophecy.
Why does the calculator floor at 1,200 kcal/day?
1,200 kcal/day is the conventional clinical floor for adult women (1,500 for men) below which most reputable nutrition guidelines recommend medical supervision. Below that intake your body responds with aggressive metabolic adaptation, micronutrient sufficiency becomes hard to maintain even with careful planning, and adherence collapses for most people within weeks. The warning isn't a hard stop — the calculator still shows the math — but it's a signal that the pace you've picked is past the safe-DIY threshold.
What happens to TDEE as I lose weight?
TDEE drops in three ways: (1) lower BMR because there's less mass to maintain (about 5 kcal/day per pound lost), (2) lower thermic effect of food because you're eating less, (3) lowered NEAT because your body conserves energy on prolonged deficits (this is the largest variable component). After 10 lb of loss you've typically lost 200–300 kcal/day from your maintenance. Recompute the calculator at your current weight to refresh the target.
Why does the timeline cap at 2 lb/week (1 kg/week)?
Past 2 lb/week, the loss is increasingly lean tissue rather than fat — the body can only mobilize fat at a finite rate, so a deficit beyond that taps muscle for energy. This is bad for body composition, athletic performance, and the rate of regain after the diet ends. The 0.5–2 lb/week range is the sustainable-loss window; if you want faster results, the only honest answer is patience.
Can I gain muscle while losing fat?
Yes, but only in specific circumstances: novice trainees, returning trainees regaining lost muscle, and individuals with significant fat to lose. For experienced lifters near their genetic ceiling, simultaneous muscle gain and fat loss is rare and slow. If you're in this last category, plan in cycles — cut to a target weight, then run a maintenance or slight surplus to gain lean mass, then cut again.
What about the surplus side — for a bulk?
Set a goal weight higher than your current weight and the calculator switches to surplus mode (the result panel shows ' kcal/day above maintenance'). The 0.5 lb/week (0.25 kg/week) default is the lean-bulk pace most strength coaches recommend — fast enough for measurable progress in lean mass, slow enough that most of the added weight isn't fat. Past 1 lb/week of gain, the proportion of fat in the gained weight rises sharply.
Why might my daily target seem high or low?
The most common cause is an over-aggressive activity-level pick on the upstream TDEE step. If 'moderately active' produces a target that doesn't match your real intake at maintenance (you're losing weight at the calculator's maintenance number), drop to 'lightly active' and recompute. The deficit math will rescale automatically — it's a function of TDEE.
Are my numbers stored or sent anywhere?
No. Every calculation runs locally in your browser. Your inputs are never transmitted — there is no server, no API call, no analytics on input values. The only state we save is your unit preference (imperial vs metric) in localStorage, shared across all our fitness tools. Estimates only — not medical advice. Consult a registered dietitian or your doctor before starting a calorie deficit, especially if you're pregnant, nursing, under 18, or have a medical condition (diabetes, eating disorder history, kidney disease).

TDEE Calculator — Total Daily Energy Expenditure

Type your stats and pick an activity level. Get the calories you actually burn day-to-day.

Macro Calculator — Daily Protein, Carbs, and Fat

Pick an activity level and a macro split. Get grams of protein, carbs, and fat per day.

BMR Calculator — Estimate Your Basal Metabolic Rate

Type your age, weight, and height. Get the calories your body burns at complete rest.