Fat Mass Index (FMI)
Fat Mass Index (FMI) is total fat mass divided by height squared (kg/m²), measured by dual-energy X-ray absorptiometry (DXA or DEXA). It expresses body fat relative to height, as BMI does for total body weight.
These percentiles are a FitnessNorms derivation from NHANES 1999-2004 DXA scans for 12,957 US adults aged 20 and over, all race and Hispanic-origin groups, using the measured DXA values and the values NCHS imputed for participants who could not be scanned; see the methodology. The NHANES scans used Hologic scanners with the Schoeller calibration; results from another DXA brand or calibration are not directly comparable.
Data source: FitnessNorms derivation from NHANES 1999-2004 DXA About this study
Reference population: US adults aged 20 and over in NHANES 1999-2004 with measured or NCHS-imputed DXA data, all race and Hispanic-origin groups
Fat Mass Index (FMI) Norms Chart by Age and Sex (kg/m²)
| Age | Sex | Percentile | ||||
|---|---|---|---|---|---|---|
| 5th | 25th | 50th | 75th | 95th | ||
| 20-24 | Male | 2.95 | 4.15 | 6.06 | 8.76 | 13.73 |
| Female | 4.81 | 6.89 | 8.75 | 12.55 | 20.36 | |
| 25-29 | Male | 3.18 | 5.31 | 7.08 | 8.90 | 14.44 |
| Female | 4.89 | 7.31 | 9.68 | 13.58 | 19.56 | |
| 30-34 | Male | 3.49 | 5.16 | 7.11 | 8.92 | 13.29 |
| Female | 5.07 | 7.50 | 9.99 | 13.36 | 20.14 | |
| 35-39 | Male | 3.81 | 5.66 | 7.31 | 9.33 | 13.63 |
| Female | 5.68 | 7.78 | 10.39 | 13.94 | 21.69 | |
| 40-44 | Male | 4.34 | 6.25 | 7.80 | 9.82 | 13.63 |
| Female | 5.54 | 8.36 | 10.91 | 13.78 | 20.33 | |
| 45-49 | Male | 4.14 | 6.33 | 7.91 | 9.36 | 13.56 |
| Female | 5.67 | 8.60 | 11.67 | 15.09 | 20.97 | |
| 50-54 | Male | 4.50 | 6.65 | 8.30 | 10.27 | 14.82 |
| Female | 6.12 | 9.01 | 11.61 | 14.59 | 20.84 | |
| 55-59 | Male | 4.27 | 6.75 | 8.26 | 10.28 | 14.35 |
| Female | 6.74 | 9.63 | 12.10 | 15.94 | 22.84 | |
| 60-64 | Male | 5.07 | 6.84 | 8.61 | 10.91 | 14.51 |
| Female | 7.38 | 9.85 | 11.99 | 15.12 | 20.85 | |
| 65-69 | Male | 5.06 | 7.31 | 8.67 | 10.96 | 15.70 |
| Female | 7.06 | 9.89 | 12.35 | 15.38 | 20.33 | |
| 70-74 | Male | 4.69 | 6.77 | 8.50 | 10.39 | 14.36 |
| Female | 6.46 | 9.63 | 12.07 | 14.31 | 18.77 | |
| 75-79 | Male | 5.28 | 7.02 | 8.53 | 10.20 | 13.05 |
| Female | 6.83 | 9.89 | 11.67 | 13.66 | 18.51 | |
| 80-84 | Male | 4.97 | 6.86 | 8.10 | 9.77 | 12.59 |
| Female | 5.86 | 8.57 | 10.61 | 13.11 | 17.56 | |
| 85+ | Male | 4.05 | 6.20 | 7.79 | 9.43 | 12.07 |
| Female | 6.15 | 8.66 | 10.27 | 12.38 | 16.59 | |
What to expect by age group
Among US adults aged 30 to 34, the middle 50% measure 5.16 to 8.92 kg/m² for men and 7.50 to 13.36 kg/m² for women. Median FMI rises from 6.06 kg/m² for men and 8.75 kg/m² for women at 20-24 to 8.67 and 12.35 kg/m² at 65-69. These percentiles show population position, not a clinical category.
| Age | Males | Females |
|---|---|---|
| 20-24 | 4.15 to 8.76 | 6.89 to 12.55 |
| 25-29 | 5.31 to 8.90 | 7.31 to 13.58 |
| 30-34 | 5.16 to 8.92 | 7.50 to 13.36 |
| 35-39 | 5.66 to 9.33 | 7.78 to 13.94 |
| 40-44 | 6.25 to 9.82 | 8.36 to 13.78 |
| 45-49 | 6.33 to 9.36 | 8.60 to 15.09 |
| 50-54 | 6.65 to 10.27 | 9.01 to 14.59 |
| 55-59 | 6.75 to 10.28 | 9.63 to 15.94 |
| 60-64 | 6.84 to 10.91 | 9.85 to 15.12 |
| 65-69 | 7.31 to 10.96 | 9.89 to 15.38 |
| 70-74 | 6.77 to 10.39 | 9.63 to 14.31 |
| 75-79 | 7.02 to 10.20 | 9.89 to 13.66 |
| 80-84 | 6.86 to 9.77 | 8.57 to 13.11 |
| 85+ | 6.20 to 9.43 | 8.66 to 12.38 |
Detailed Breakdowns
Select an age group and sex below for detailed percentile charts and distribution labels.
Frequently Asked Questions
How is FMI calculated from a DEXA scan?
Divide total fat mass in kilograms, as reported by the DXA scan, by height in metres squared. A person with 20 kg of fat mass and a height of 1.75 m has an FMI of 20 / (1.75 x 1.75) = 6.53 kg/m².
Can I compare my DEXA report to these values?
Only approximately. DXA results depend on the scanner brand, software and calibration. These values come from Hologic scanners using the Schoeller calibration in NHANES 1999-2004. A GE Lunar scan, or a Hologic scan with a different calibration, can report a different fat mass for the same body, so a small difference from these percentiles may reflect the scanner rather than the body.
What is a healthy FMI?
These percentiles show where a value sits in the US population, not a clinical category. Kelly et al. 2009 propose FMI classification ranges matched to the prevalence of the WHO BMI categories, in Table 4 of Kelly et al. 2009. Interpret an individual value with a clinician.
How do these values relate to Kelly et al. 2009?
Kelly et al. 2009 fitted separate reference curves for non-Hispanic White, non-Hispanic Black and Mexican American adults from the same NHANES scans. This page pools all US adults, as the site's other NHANES measures do, so its values differ from any one of Kelly's curves. The method behind it reproduces the National Center for Health Statistics' own published percentiles for the same survey years; see the methodology.