The body fat calculator that
tells you what to aim for
Any calculator can label where you are. This one gives you a healthy target band for your age and sex, a suggested number inside it, and the weight that target lands you at with your muscle held.
Body Fat Calculator
A healthy target for your age, and what it means on the scale
17.5%
YOUR BAND · MEN · AGE 45 · LONGEVITY
15–20% body fat
You are around 31.3% now, above the band. To reach 17.5% you would lose 26–48 lb of fat while holding your 142–160 lb of lean mass.
FIRST STOP · TOP OF BAND (20%)
178–200lb
WEIGHT AT 17.5% · LEAN HELD
172–194lb
The weight is a projection, not the goal: it assumes every lb you lose is fat. Holding the lean side of that assumption is what protein and lifting are for.
CURRENT BODY FAT IS ESTIMATED, AND THE RANGE ON THE OUTPUTS IS SIZED TO THAT ESTIMATE.
Where the weight goes if you retain lean muscle mass
Your weight is the two blocks added together. Only one of them changes.
NOW · 31.3% BODY FAT
220 lb
AT YOUR TARGET · 17.5% BODY FAT
183 lb
THE TEAL BLOCK IS IDENTICAL IN BOTH BARS. EVERYTHING THE SCALE GIVES UP IS AMBER. THAT IS WHY THE WEIGHT IS A PROJECTION AND THE LEAN LINE IS THE RESULT.
Disclaimer: This calculator turns published, age-banded reference ranges into a target band and a projection. The output is a target, not a prescription, and not medical advice. It is not intended for people who are pregnant, under 18, or managing a condition that affects body composition. Talk to your provider before changing how you eat or train.
Updated August 31, 2026
IN SUMMARY
There is no single ideal body fat percentage. There is a healthy range that rises with age and runs roughly ten points higher for women, and a sensible target sits in the middle of your slice of it. For a man of 40 to 59 the published healthy range is about 11–22% and this body fat calculator suggests a 15–20% band; for a woman the same age the range is about 23–34%, and the band 22–29%. Two rules make the number honest. The target is a fat-mass goal with your lean mass held: the projected weight assumes you keep the muscle, which is what your protein target and lifting are for. And the number is instrument-specific: the bands are DEXA-referenced, and a body-composition scale reads the same body lower. Lower is not better, either; the selector stops at 8% for men and 15% for women.
What the calculator is doing
- 01
Your band comes from sex, age and objective
The same table the app's Goals engine runs: rows step at 40 and 55, and a longevity aim sits a few points above a performance one. No un-aged category chart.
- 02
The suggested target is the middle
Evidence anchors the band's edges, not a best point inside it, so the default is the midpoint, the same default the app opens on. The slider stays in the band, never below the essential-fat buffer.
- 03
Weight is a projection, not the goal
The goal is fat mass. Projected weight divides your lean mass by one minus the target, so it is only true if the muscle stays: that assumption is the whole game.
- 04
The tabs buy precision, not a different band
Basic estimates your current body fat from height, weight and sex. Smart takes your scale's percent with the engine's three-point slop. Advanced takes the fat-mass line off a DEXA report.
Three numbers behind the bands
The ranges here are not a fitness chart. They anchor to reference studies, and every number traces to the sources below.
The reference approach maps body-fat percentage onto the established BMI cutoffs, so the ranges inherit the evidence behind them. Women the same age: about 23–34%. Both rise with each age row.
National DEXA data put the BMI-25-equivalent body fat for men at 22.6 to 28.0% across age and ethnic groups, a few points above the four-compartment numbers: same body, higher-reading method.
Pooled trials that added resistance training to lifestyle change reported 17.5% of the loss coming from lean mass, against 26.2% in trials that did not add one. A target is only met honestly when the loss is fat.
How the body fat calculator sets your band
The band table is the one the app uses, rendered from the same code the calculator runs. Sex sets the frame: women carry roughly ten points more essential fat than men, so every band sits higher. Age moves the rows, because the healthy range genuinely climbs as muscle declines and fat redistributes. The objective picks the lane: longevity is the comfortable aim; performance sits a few points leaner for people who train for it.
| Age | Men · longevity | Men · performance | Women · longevity | Women · performance |
|---|---|---|---|---|
| 20–39 | 12–18% | 10–15% | 20–27% | 18–24% |
| 40–54 | 15–20% | 12–17% | 22–29% | 20–26% |
| 55+ | 17–22% | 14–19% | 24–31% | 22–28% |
DEXA-frame percentages from the app's Goal Engine, inside the published healthy ranges. The floor under every target is 8% for men and 15% for women: a deliberate buffer above essential fat, the share your body physically requires. Targets, not prescriptions.
The bands are deliberately narrower than the full healthy range: classification tells you where risk changes, and a target is the place inside it worth steering for. The field is moving the same way. A 2025 Lancet commission recommended confirming obesity itself with a body-fat measure rather than BMI alone, which is the premise of setting goals in body-fat terms.
Why lower is not better
A body-fat percentage is a ratio, and a ratio can be satisfied the wrong way. Lose muscle while keeping fat and the percent barely moves; lose both and it can drift down while you get weaker. So every projection here holds your lean mass, and the honest pairing for any target on a GLP-1 is the split of your planned loss and enough protein to defend it.
Below the band, the case runs out. The selector stops at 8% for men and 15% for women, a margin above essential fat: past that point it is aesthetics with mounting cost. And if the plan is rapid weight loss, the lean edge of your band is the wrong first stop anyway: keeping the muscle is what makes the target worth hitting.
The percent depends on the instrument
The same body reads differently on different tools. The bands here are DEXA-referenced; a body-composition scale, the kind that runs a small current through you and estimates fat and lean rather than just weight, tends to read three to five points lower, sometimes more. That gap is method, not progress. A scale percent on the Smart tab carries the engine's three-point slop; the fat-mass line from a DEXA report on Advanced tightens to a point.
The practical rule: pick one instrument and compare it with itself. A scale that is loose on the absolute number can still be reliable on direction, which is what matters week to week. The full comparison lives on DEXA versus smart scale.
What the target means in pounds
The projection is one line of arithmetic: take your lean mass, everything that is not fat, and divide by one minus the target. A 214 lb man at 27% carries about 156 lb of lean; a 15% target implies about 184 lb, all 30 lost pounds fat. If he adds muscle along the way, the weight lands higher and the target is still met: that is why the goal is fat mass and the scale number is a forecast. It is also how the tracker charts it: fat and lean on separate lines, so you watch the assumption hold rather than take it on faith.
Setting a target versus watching it arrive
The calculator is a well-sourced assumption about people like you. The app is a record of you: it reads fat and lean from a body-composition scale through Apple Health, anchors them with imported DEXA scans, and shows the target against what is actually happening.
- Give you an age- and sex-banded target instead of one chart for everyone
- Project the weight a target implies, with lean mass held
- Size its own uncertainty to how you measured yourself
- Fat mass and lean mass held apart, never merged into one total
- Readings sync in from a compatible body-composition scale through Apple Health
- DEXA scans imported as anchor points, so drift from the scale is visible
Where these numbers come from
- 01
Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index
The American Journal of Clinical Nutrition · 2000 · Gallagher D, Heymsfield SB, Heo M, et al. Am J Clin Nutr. 2000;72(3):694–701. PMID 10966886
- 02
The American Journal of Clinical Nutrition · 2012 · Heo M, Faith MS, Pietrobelli A, Heymsfield SB. Am J Clin Nutr. 2012;95(3):594–602. PMID 22301924
- 03
Definition and diagnostic criteria of clinical obesity
The Lancet Diabetes & Endocrinology · 2025 · Rubino F, Cummings DE, Eckel RH, et al. Lancet Diabetes Endocrinol. 2025;13(3):221–262. PMID 39824205
- 04
British Journal of Nutrition · 2023 · Siedler MR et al. Br J Nutr. 2023;130(5):827–840. Full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC10404482/
- 05
Diabetes, Obesity and Metabolism · 2026 · Eisa N, Barood O. Diabetes Obes Metab. 2026;28(6):4818–4827. doi:10.1111/dom.70666
Body fat targets, answered
What body fat percentage should I aim for?
The middle of your band. For a man of 45 aiming at longevity that band is 15–20%, so around 17–18%; for a woman the same age it is 22–29%, so around 25–26%. The bands step up at 40 and again at 55, because the healthy range genuinely rises with age.
Is 15% body fat good for a man over 40?
Yes. It is the lean edge of the 15–20% longevity band for 40 to 54, well inside the published healthy range. It is also the harder end to hold during rapid weight loss, so pair it with protein and lifting rather than crash toward it.
Why does the healthy range rise with age?
Because bodies change. Muscle declines and fat redistributes with age, and the reference studies found older age independently associated with higher body fat at the same BMI. A target that ignores age is too lax at 25 and needlessly punishing at 65.
Should I just aim as low as possible?
No. Below the band there is no added health case, only cost: the calculator will not set a target under 8% for men or 15% for women. And chasing very low body fat during rapid loss is the worst timing there is; lean mass is already the thing under pressure.
My smart scale and my DEXA report disagree. Which do I enter?
Whichever you have, on its own tab. The bands are DEXA-referenced, and a body-composition scale often reads several points lower on the same body, so the Smart tab widens its outputs. Pick one instrument and judge progress against itself.
Does the target change on a GLP-1?
The band does not; the discipline around it does. A body-fat percentage is a ratio, and losing muscle moves it the same way as losing fat. On a GLP-1, where a quarter or more of the loss can be lean, the target only means something with lean mass held.
The calculator sets the target. The app shows it arriving.
Bild Health keeps fat mass, lean mass, protein, training and your dose history in one record — the lean number measured from your scale, anchored by imported DEXA scans.
Lose the fat. Keep the muscle.