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Weight loss calculator: calories and weeks to your goal

A weight loss calculator that sizes daily calories and estimates weeks to goal weight from Mifflin-St Jeor TDEE and your weekly pace.

Units
Sex
Activity level

Target body weight, not a medical ideal.

Faster than about 0.5–1% of body weight per week is usually a poor trade for muscle and adherence.

Rapid weight-loss goals can be a warning sign of disordered eating. This timeline is educational, not a medical weight-loss program.

What this tool does

This weight loss calculator estimates your TDEE from height, weight, age, sex, and activity, then sizes a daily calorie target to match your chosen weekly kg pace and divides the gap to goal weight by that pace for a week count.

How it works

Pick a goal weight and weekly loss pace (0.15–0.75 kg/week). The tool computes Mifflin-St Jeor TDEE, calculates the daily deficit for that pace (weekly kg × 7,700 ÷ 7), caps the deficit near 25% of TDEE, applies an educational calorie floor, and reports target calories plus weeks to goal. Imperial users enter goal pounds; math stays metric internally.

Formula and methodology

TDEE = Mifflin-St Jeor BMR × activity factor. Daily deficit = weeklyKg × 7,700 ÷ 7 (≈440 kcal/day at 0.4 kg/week). Target = max(TDEE − deficit, 1,200 kcal female / 1,500 kcal male floor). Weeks ≈ |current weight − goal| ÷ weeklyKg. Pace is clamped to 0.15–0.75 kg/week.

How to interpret the result

The week count is a planning sketch, not a deadline. Plateaus, water shifts, and metabolic adaptation stretch real timelines. If the calorie floor triggers, your pace outruns what this page will fund — lower the weekly kg instead of eating below the floor. Keep protein in the deficit band (roughly 1.6–2.2 g/kg) throughout.

Example

Worked example: 80 kg, 175 cm, age 35, male, lightly active → Mifflin-St Jeor TDEE ≈ 2,760 kcal. Goal 75 kg at 0.4 kg/week needs ~440 kcal/day deficit (0.4 × 7,700 ÷ 7). Target ≈ 2,320 kcal. Five kg to goal ÷ 0.4 = about 13 weeks on paper. Re-run when the weekly average lands near 75 kg, not after one low weigh-in.

Common mistakes

  • Copying a goal weight from a BMI chart built for someone else's height.
  • Choosing 0.75 kg/week on a 60 kg frame — that is a large fraction of body weight, not a sustainable hobby.
  • Leaving current weight stale after you have already lost 4 kg on the scale.
  • Treating the week count as a deadline you must punish yourself to hit.

When this estimate may be off

  • Goal weight sits below a healthy range for your frame — the tool cannot judge that.
  • Weekly kg is a wish, not a deficit you will actually eat day to day.
  • Edema, medication, or menstrual-cycle water dominate the scale.
  • TDEE is inflated because activity in the dropdown was theater.

Frequently asked questions

How do I calculate weight loss?

Estimate TDEE (Mifflin-St Jeor × activity), pick a weekly kg pace, and size a daily deficit: weekly kg × 7,700 ÷ 7. This calculator does that math and divides your gap to goal weight by the pace for a week count.

How many calories should I eat to lose weight?

Enough below TDEE to match your weekly pace, without dropping under the educational floor (1,200 kcal female / 1,500 kcal male). At 0.4 kg/week, that is roughly a 440 kcal/day gap — but the exact number depends on your TDEE.

How long will it take to reach my goal weight?

Weeks ≈ |current weight − goal| ÷ weekly kg pace. An 80 kg person heading to 75 kg at 0.4 kg/week is about 13 weeks on paper. Real timelines run longer with plateaus, holidays, and water shifts.

What is a realistic weekly weight loss goal?

Many adults do well near 0.25–0.5 kg/week (about 0.5–1% of body weight). Faster than that often costs lean mass, training quality, and adherence. The form caps pace at 0.75 kg/week as an educational brake.

Can I use pounds instead of kilograms?

Yes. Toggle imperial units and enter goal weight in pounds. Weekly pace is still entered in kg/week on this form — 0.4 kg/week is roughly 0.9 lb/week.

How accurate is this weight loss estimator?

It is a planning estimate, not a guarantee. Mifflin-St Jeor predicts groups better than individuals, the 7,700 kcal/kg rule is a shortcut, and bodies adapt. Use two-week weight averages and re-run when TDEE changes.

Does this include exercise calories?

Only through the activity factor on TDEE. Do not subtract a treadmill readout on top unless that activity was not already in the dropdown.

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