Nutrition · Free calculator

Weight Loss Timeline Calculator

See how many weeks it takes to reach a goal weight at your chosen deficit, with metabolic adaptation factored into the curve.

Short answer

Weight Loss Timeline Calculator

43Weeks to goal

Without accounting for metabolic adaptation you'd predict 40 weeks — the real number is closer to 43 because a lighter body burns less. Plan two maintenance weeks per 12 weeks of dieting; they barely change the timeline and dramatically improve the odds you finish.

How it's calculated: 40 lb to lose at about 0.94 lb/week ≈ 9.8 months. Adjust the inputs below to recalculate for your own numbers.

Disclaimer: Educational estimate only — not medical advice, diagnosis, or treatment. Population formulas do not account for your individual physiology, medications, or medical history. Discuss any health decision with a licensed clinician, and seek immediate care for urgent symptoms.

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220
180
500
12%

How much the deficit shrinks as you get lighter.

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Formula used

Adaptation-adjusted timeline

The naive 3,500-kcal rule assumes a fixed deficit forever. Halving the stated adaptation approximates the average penalty across the whole diet, since it builds gradually as weight falls.

Weeks = (lb to lose × 3,500) ÷ (deficit × (1 − adaptation ÷ 2) × 7)
1 lb fat
≈3,500 kcal
Typical adaptation
10–15%
Recommended breaks
2 wks per 12
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The curve flattens — plan for it

Weight loss is never linear. The first two weeks include a glycogen and water drop that exaggerates progress, and the final ten pounds always take longer per pound than the first ten because the same deficit is a bigger share of a smaller maintenance.

  • Recalculate your deficit every 10–15 lb lost.
  • Expect 2–4 week plateaus even with perfect adherence.
  • Judge progress by a 7-day rolling average, never a single weigh-in.

FAQ

How long does it take to lose 20 pounds?

At a 500 calorie daily deficit, roughly 22–26 weeks once metabolic adaptation is factored in. A 750 calorie deficit compresses that to about 15–18 weeks but is harder to sustain.

Why did my weight loss stall?

Usually a mix of a smaller body needing fewer calories, unmeasured portion creep, and water retention. Recalculate maintenance and tighten tracking for two weeks before cutting further.

Is faster weight loss bad?

Rapid loss beyond about 1% of body weight per week increases muscle loss, gallstone risk, and rebound. Heavier individuals can safely tolerate a faster absolute rate.

How this calculator is built

Independently maintained

Written by Sam Doshi and the RevenueLab editorial team. We don't sell the data feeds this tool is built on.

Sourced from primary data

Benchmarks come from public AdSense / Stripe / IRS disclosures and reader-submitted data — never third-party "$X per view" claims. Full methodology.

Last editorial review

Reviewed on a rolling quarterly cycle. Dated reviews are published on the methodology record for each calculator.

Editorial standards

See our editorial policy and disclaimer. Results are estimates, not advice.

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