Calorie Calculator for Weight Loss

How the calculator works backward from your goal

This page runs the opposite direction of deficit-based planning — it starts at the finish line:

1. Your maintenance (TDEE) from the Mifflin-St Jeor equation, using your stats and activity level.
2. Required daily deficit = (current − goal) × 3,500 ÷ (weeks × 7). In the example: 30 lbs × 3,500 ÷ 168 days = 625 calories a day.
3. Daily intake target = maintenance − deficit: 2,079 − 625 ≈ 1,454 calories a day.

To plan forward from a deficit instead ("I'm eating 500 less — when do I arrive?"), use the calorie deficit calculator.

How fast is too fast?

Common guidance puts healthy weight loss at 0.5–2 lbs per week, and this calculator checks your plan against two lines:

• The pace line: if your implied rate exceeds 2 lbs a week, you get a warning. Very fast loss pulls a larger share from muscle and water, and the hunger is harder to sustain — that's physiology, not willpower.
• The intake floor: if the computed target falls below 1,200 calories (women) or 1,500 (men), you get a warning. Below those levels, covering basic nutrition gets difficult and belongs under medical supervision.

Pass both and you see a green confirmation; trip either one and the calculator tells you the fastest advisable timeframe instead (say, 22 weeks instead of 16) — far more useful than a bare "not recommended."

What to do when the deadline arrives and you're not there

Almost nobody lands exactly on target, and here's why: the 3,500-calorie rule is a static approximation. As you get lighter your maintenance drops and the original deficit quietly shrinks; your body also trims everyday movement. Expect 80–90% of the plan as a normal outcome — losing 24–27 of a planned 30 lbs in 24 weeks is a success, not a failure.

The standard move at that point: put your new weight back into the calculator (maintenance has changed) and run another leg at the new target. Recalculating every 10 lbs is the routine maintenance of this method.

How to use this calculator

1. Switch imperial/metric, then enter sex, age, height, and current weight.
2. Enter your goal weight and timeframe in weeks — if you're unsure, try 16–26 weeks first.
3. Pick your activity level (when in doubt, choose one lower).
4. Read the result: what to eat each day up top, then maintenance, the required deficit, and your implied weekly pace.
5. Check the verdict bar: green means the plan sits within commonly recommended bounds; amber means it's too fast — adjust to the alternative timeframe shown.

Frequently asked questions

How many calories should I eat a day to lose weight?

The generic answer: maintenance minus 500–750 calories. The example above lands at 1,454; a man maintaining on 2,600 would eat roughly 1,900–2,100. Below 1,200 (women) or 1,500 (men) calories a day is medically supervised territory, not a DIY target. Computing from your own stats and goal beats memorizing generic numbers.

How much weight can you safely lose in a week?

Common guidance is 0.5–2 lbs per week (roughly 0.5–1% of body weight). Heavier people can sit near the top early on (some of it water); the closer you get to goal, the more you should drift toward the bottom — planning the last 10 lbs at 0.5–1 lb a week is kinder to your muscles and your mood.

What happens if I only eat 1,200 calories a day?

For most adult women that's a commonly cited floor, not a goal — the threshold where covering basic nutrition is still feasible. Sustained intake below it commonly brings fatigue, declining workout quality, muscle loss, and rebound eating. When the calculator computes below the floor it offers an alternative timeframe — taking the longer timeline is almost always the better trade.

I'm eating the target and not losing — why?

The three usual causes: logging gaps (drinks, sauces, weekend meals — people commonly underestimate by 20–30%), an activity level set one notch too high ("gym three times a week" with otherwise sedentary days is closer to light than moderate), and water weight hiding fat loss (judge by 2–4 week averages, never single days). If none of those fixes it, drop one activity level and recalculate.

Can I lose weight without exercising?

Yes — a calorie deficit is sufficient for fat loss on its own. But exercise, strength training especially, decides whether the weight you lose is fat or muscle, and it keeps your maintenance from sinking. The winning combination: diet for the deficit, protein to protect muscle (1.6–2.2 g/kg — see the macro calculator), and lifting to give your body a reason to keep it.

How do I keep the weight off after I reach my goal?

Build a maintenance phase into the plan from day one: at goal, raise intake to your new maintenance (re-enter your new weight and pick maintain) and hold your weight there for 4–8 weeks before deciding whether to cut further. Most regain happens when people sprint to the finish and immediately return to old eating — maintenance is a skill you practice, not a default state.

Data sources: The 3,500 kcal ≈ 1 lb conversion is a rule-of-thumb approximation; pace and intake-floor limits are commonly cited public-health values; maintenance uses the Mifflin-St Jeor equation (published research, 1990). Every example number was computed by this page's calculator — the female example is the calculator's default input, so you can reproduce it exactly. Related tools: calorie deficit 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.