The body fat calculator that
helps you set your goals
Body Fat Calculator
A healthy target for your age, and what it means on the scale
Note: we strongly recommend setting your body fat goal based on a measurement of your body fat % today, using the Smart or Advanced tabs above. A DEXA scan is the most accurate, and a smart scale is much better than nothing.
30%±5% (25% TO 35%)
Estimated from height, weight, age and sex with our DEXA-calibrated algorithm.
Your band is 15 to 20% for a man of 45 aiming at longevity. It comes from the sex, age and aim above, and the slider starts in the middle.
17.5%
STEP 3 · YOUR GOAL WEIGHT RANGE AT 17.5%
SCALE LANDS NEAR · LEAN HELD
188lb±13 (174 TO 201 LB)
A range, not a single number. It carries the ±5% of the estimate, and both ends assume you hold the lean mass you have. Build muscle on the way and the scale lands above it, with the target still met. Holding the lean side is what protein and lifting are for.
CURRENT BODY FAT IS ESTIMATED, NOT MEASURED, SO EVERY OUTPUT CARRIES A MARGIN OF ERROR OF ±5 POINTS. A SCALE READING OR A SCAN REPLACES IT.
Where the weight goes if you hold your lean mass
The same 17.5% target from each edge of the estimate. Leaner now means more lean mass to keep, so the scale lands heavier.
IF BODY FAT % IS 25% NOW · LOW EDGE OF THE ESTIMATE
201 lb
IF BODY FAT % IS 30% NOW · MIDPOINT · THE NUMBER WE SHOW
188 lb
IF BODY FAT % IS 35% NOW · HIGH EDGE OF THE ESTIMATE
174 lb
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.
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. 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.
- 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.
- 04
The tabs buy precision, not a different band
Basic estimates from height, weight, age and sex with our own fit to 5,020 DEXA scans, printed with its ±5 points range. Smart takes your scale's percent with a three-point margin of error. Advanced takes the percent off a DEXA report.
Three numbers behind the bands
Not a fitness chart: every number traces to the studies 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%.
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: higher-reading method, same body.
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, because women carry roughly ten points more essential fat; age moves the rows; the objective picks the lane.
| 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-based percentages from the app's Goal Engine, inside the published healthy ranges. No target goes below 8% for men or 15% for women, a deliberate buffer above essential fat. Targets, not prescriptions.
The bands are deliberately narrower than the full healthy range: classification tells you where risk changes, a target is the place inside it worth steering for. A 2025 Lancet commission recommended confirming obesity 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 ratio can be satisfied the wrong way: lose both tissues and the percent drifts 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: past the 8% and 15% floors it is aesthetics with mounting cost. And if the plan is rapid weight loss, the lean edge of your band is the wrong place to aim first 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-based (the reference data behind them are on The Science); 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 a three-point margin of error; the percent from a DEXA report on Advanced needs none.
Basic has no instrument, only your height, weight, age and sex. Our fit to 5,020 scans from NHANES 2015–2018 lands within ±5 points four times in five, and five points spans most of a band. So it gives you the range, its midpoint, and the direction: about nine in ten adults aged 20 to 59 measure above their band top, and from a BMI of 25 that is where height and weight put you too.
The practical rule: pick one instrument and compare it with itself. Loose on the absolute number is still reliable on direction, the thing that matters weekly. 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. Add muscle along the way and the weight lands higher with the target still met, which is why the goal is fat mass. 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: fat and lean read from a body-composition scale through Apple Health, anchored by imported DEXA scans, against the target.
- Give you an age- and sex-banded target instead of one chart for everyone
- Project the weight a target implies, with lean mass held
- Show a range and a direction where an estimate cannot honestly give a number
- 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. PMID 41877354.
- 06
A six-constant estimator of fat-free mass from height, weight, age and sex, fit to NHANES whole-body DEXA
Bild Health · 2026 · Bild Health methods paper, 2026. In preparation; constants and evaluation on file
- 07
NHANES 2017–2018 Dual-Energy X-ray Absorptiometry: Whole Body
Centers for Disease Control and Prevention, National Center for Health Statistics · 2021 · NHANES 2017–2018 examination file DXX_J, documentation and codebook
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.
How does the Basic tab work out my current body fat?
With our own formula, fit to 5,020 DEXA scans from the national health survey. It lands within ±5 points four times in five, which is too loose to call a number on its own, so the tab prints the midpoint with its margin of error attached and the range it spans. A scale reading or a scan replaces it with a measurement.
My smart scale and my DEXA report disagree. Which do I enter?
Whichever you have, on its own tab. The bands are DEXA-based, and a body-composition scale often reads several points lower on the same body, so the Smart tab adds a margin of error. 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 is measured from your scale, anchored by imported DEXA scans.
Lose the fat. Keep the muscle.