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Fat loss timeline calculator: estimate time to goal weight
A rough timeline and daily deficit for reaching a target body-fat percentage.
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Short answer: At a steady 0.5–1% of bodyweight a week, the calculator projects the weeks and daily deficit to reach your target, assuming all loss is fat at about 7,700 kcal per kg.
- Fat to lose
- 7.7 kg
- Target weight
- 82.3 kg
- Estimated time
- 12 weeks
- Daily deficit at the start
- 742 kcal
How the weeks could look
Starting at 90 kg and reaching about 82.3 kg after roughly 12 weeks, if the weekly rate holds. Real weight moves in steps rather than a smooth line, so judge progress on a weekly average.
What if you went slower or faster?
| Weekly loss | Time | Daily deficit | Use |
|---|---|---|---|
| 0.5% | 18 weeks | 495 kcal | |
| 0.75% (yours) | 12 weeks | 742 kcal | |
| 1% | 9 weeks | 990 kcal |
Assumes every kilogram lost is fat and uses the approximation that 1 kg of body fat holds about 7,700 kcal. Real loss is rarely this steady, and some lean mass may be lost too. Your body figures stay on this device so the Hub's other calculators can fill them in for you, and are never sent anywhere.
How long does it take to lose fat? How the timeline is worked out
The calculator keeps your estimated fat-free mass the same, works out the bodyweight that matches your target body-fat percentage, then takes off your chosen percentage of bodyweight each week until it gets there. The number of weeks it takes is your timeline.
Because each week is a percentage of a slightly smaller body, the weekly amount falls a little as you go.
Safe and realistic weekly fat loss: 0.5% to 1% of bodyweight
Losing about 0.5–1% of bodyweight a week is a common evidence-based range for people who train and want to keep muscle (Helms et al., 2014). Slower rates need a smaller deficit and are usually easier to sustain.
Why weight loss slows down over time
A lighter body uses less energy, and day-to-day water changes can hide fat loss for a while. The calculator assumes a steady rate, so real progress will be less even. Recheck your maintenance calories as your weight drops and judge progress on a two to three week average.
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How the calculation works
Estimated fat-free mass is held constant. Target weight is that mass divided by (1 − target body-fat percentage ÷ 100). The model then reduces the remaining bodyweight by the selected percentage each week until it reaches the target. The starting deficit uses the existing approximation of 7,700 kcal per kg of fat.
Worked example
At 90 kg and 25% body fat, a target of 18% with a chosen loss rate of 0.75% a week gives a modelled target weight of 82.3 kg, 7.7 kg to lose and 12 weeks. The starting deficit estimate is 742 kcal a day; this is an arithmetic example, not a personal prescription.
What the result cannot tell you
The model assumes all weight lost is fat and that the selected rate continues steadily. Real changes include water and sometimes lean tissue, energy expenditure changes, and body-fat measurements contain error. The week count is a projection, not a deadline or guaranteed outcome.
Frequently asked questions about fat loss timelines
Is the predicted completion week guaranteed?
No. It is the result of the selected steady-rate model. Actual progress will not follow an exact weekly schedule.
Does the tool predict muscle loss?
No. It holds fat-free mass constant, which is an assumption rather than a promise.
Can I enter a target weight directly?
This page calculates target weight from current and target body-fat percentages. Its inputs do not include a separate target-weight field.
How big should my calorie deficit be?
The calculator sets the deficit from your chosen rate: 0.5–1% of bodyweight a week, at about 7,700 kcal per kg. A slower rate means a smaller deficit.
Why has my scale weight stalled in a deficit?
Day-to-day water and food weight can hide fat loss for a week or more. Judge progress on a two to three week average, not a single weigh-in.
How do I keep muscle while losing fat?
Keep lifting with resistance training, eat enough protein and avoid losing weight faster than about 1% of bodyweight a week.
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Educational information for adults aged 18 and over. It does not diagnose, treat or manage any medical condition. If you have a health condition, or symptoms that worry you, speak to your doctor or a health professional.