Calorie Deficit Calculator

How the calculator projects your timeline

Three steps, all reproducible:

1. Your maintenance (TDEE) comes from the Mifflin-St Jeor equation applied to your stats and activity level — the same engine as our TDEE calculator.
2. Pick a deficit: 250 (gentle, ~0.5 lb/week), 500 (steady, 1 lb), 750 (fast, 1.5 lb), or 1,000 (aggressive, 2 lb) calories a day. Your daily intake target = maintenance − deficit.
3. The timeline applies the 3,500-calorie rule: weeks to goal, plus a milestone table of projected weights.

Worked example: 2,576 − 500 = 2,076 calories a day; 20 lbs × 3,500 ÷ (500 × 7) = 20 weeks, with projected weights of 198 / 196 / 192 / 188 / 184 / 180 at weeks 2 through 20.

Want the inverse — "I want to lose 15 lbs in 16 weeks, what do I eat?" — that's goal-based reverse planning, on the weight loss calorie calculator.

Choosing among the four deficit levels

A bigger deficit is faster, but the costs aren't linear:

• 250 cal/day: barely noticeable — one soda and half a snack. Right for leaner people who don't want training to suffer; the catch is patience (20 lbs takes ~40 weeks).
• 500 cal/day: the most-recommended level in both research and practice, and the balance point between pace and sustainability. The default for most people.
• 750 cal/day: hunger is real, training quality starts to dip, and muscle loss becomes a risk. Best used short-term by people with more to lose.
• 1,000 cal/day: two pounds a week, the commonly advised speed limit. Intake can easily fall below the minimum floor (1,200 cal for women, 1,500 for men — the calculator shows a warning bar if yours does), and hunger plus fatigue tests compliance.

Pick the level you can hold for 20 weeks, not the one that's fastest on paper. The classic failure script is an aggressive start followed by a week-three collapse.

Why real progress runs slower than the projection

You'll notice it within a month: the first two weeks beat the projection (water weight), then progress drifts behind it. The calculator isn't broken — the 3,500-calorie rule is a static approximation, and your body adapts:

• Metabolic adaptation: as you get lighter, maintenance drops (a smaller body burns less), quietly shrinking your original 500-calorie gap.
• NEAT decline: when you eat less, you move less without noticing — fewer steps, less fidgeting — which can cost a couple hundred calories a day.
• Water noise: salt, carbs, and hormonal cycles can swing your weight 2–4 lbs, completely hiding a week of fat loss.

The right way to use the tool: recalculate every 10 lbs lost (your maintenance has changed), and judge progress by your 2–4 week average, never a single morning's reading.

How to use this calculator

1. Switch imperial/metric, then enter sex, age, height, current weight, and goal weight.
2. Pick your activity level (when in doubt, go one lower — most people overestimate).
3. Choose a daily deficit and read the result: what to eat each day up top, then maintenance, deficit, weekly pace, and weeks to goal.
4. Open the week-by-week projection for milestone weights, and the four-level comparison to see what switching levels buys you (current level highlighted).
5. If the intake floor warning appears, step down to a smaller deficit.

Frequently asked questions

What is a calorie deficit?

The gap between the calories you burn in a day and the calories you eat. Burn 2,500, eat 2,000, and you're running a 500-calorie deficit. A deficit can only come from two places — eating less, moving more, or both — and for most people the eating side contributes far more (one muffin ≈ a 45-minute jog).

How much deficit does it take to lose a pound?

The standard approximation is a cumulative 3,500 calories per pound of fat — a 500-calorie daily deficit, one pound per week. It's a rule of thumb, not physics: early loss runs faster (water), long-term loss slower (metabolic adaptation). Use it as a planning baseline, not a promise.

Is a 1,000-calorie daily deficit safe?

It sits at the commonly advised speed limit of 2 lb/week and suits people with more weight to lose — but check where it leaves your intake first. With 2,500 maintenance, a 1,000 deficit leaves 1,500, which is below the floor for women. The calculator warns when that happens; drop to the 500–750 range instead.

Why am I not losing weight in a deficit?

Rule out three things first: water retention (a salty, high-carb day can add 2–3 phantom pounds — watch weekly averages), undercounted intake (sauces, drinks, and weekend "relaxed" meals are the usual suspects; people commonly underestimate by 20–30%), and an activity level set one notch too high. If all three check out, your true maintenance is lower than the estimate — drop a level and recalculate.

Does exercise count toward my deficit?

Don't count it twice: the activity level already folds your regular workouts into the maintenance estimate. Keep your routine as is, and resist eating back "30 extra minutes of running" — fitness trackers notoriously overestimate burn, and eating it back erases the deficit.

How do I break a weight loss plateau?

A plateau almost always means maintenance fell but intake didn't. Recalculate your TDEE and target every 10 lbs; audit your logging, weekends included; keep protein and sleep high. If your two-week average is truly flat, add 100–200 calories to the deficit — or eat at your new maintenance for a week (a "diet break") before continuing.

Data sources: The 3,500 kcal ≈ 1 lb conversion is the standard rule-of-thumb approximation (originating with Wishnofsky, 1958, and framed as an approximation throughout this page); maintenance uses the Mifflin-St Jeor equation (published research, 1990); intake floors are commonly cited public-health values. Every example number was computed by this page's calculator — the male example is the calculator's default input, so you can reproduce it exactly. Related tools: weight loss calorie calculator, TDEE calculator, macro calculator, all health calculators.

Disclaimer: This calculator uses published estimation methods. Results are estimates for reference only and are not medical or nutritional advice. If you are underweight, pregnant or nursing, have a history of disordered eating, or have diabetes or another metabolic condition, consult a physician or registered dietitian before starting a weight loss plan.