Methodology
This page documents the exact formula, source, units, rounding, input bounds, and worked examples for every calculator on this site. Each section describes what the live calculator actually does — where this page and a calculator ever disagree, that is a bug, and you can report it via the Report an Error page.
Current standard — WHtR (Army Directive 2026-13)
WHtR = waist ÷ height (both in the same unit) Within the standard if WHtR < 0.55 (strictly less than) max_waist_in = height_in × 0.55 buffer_waist_in = height_in × 0.52
Units: the official Army implementation takes inches; centimeters for both values produce an identical ratio. The threshold is gender-neutral and age-neutral. Source: Army Directive 2026-13 (effective July 7, 2026), cited via armyresilience.army.mil — full citation on the Sources page.
Comparison rule (important): the pass check runs on the full-precision ratio — never on the rounded display value. A true ratio of 0.5499 meets the standard even though it displays as “0.550”. The calculator adds a “very close to the threshold” note for ratios in [0.5495, 0.55) because measurement technique matters at that margin.
Worked examples (also shown on the homepage):
- 5′10″ (70 in) + 36 in waist → 36 ÷ 70 = 0.514 — within standard
- 5′4″ (64 in) + 36 in waist → 36 ÷ 64 = 0.563 — above standard
- 6′0″ (72 in) + 40 in waist → 40 ÷ 72 = 0.556 — above standard
Display: three decimal places, rounded half away from zero. Max waist is shown rounded to the nearest ½ inch; the buffer (0.52 comfort margin) uses the same rule.
Legacy single-site tape (June 2024 – July 2026)
Male: %BF = -26.97 − 0.12 × weight + 1.99 × abdomen Female: %BF = -9.15 − 0.015 × weight + 1.27 × abdomen
Formulas cited verbatim from ALARACT 053/2024 and ALARACT 046/2023. Units: weight in pounds, abdomen circumference in inches. Display: two decimal places, rounded half away from zero. Pass judgment compares the estimate to the archived age-group maxima (male: 20% / 22% / 24% / 26%; female: 30% / 32% / 34% / 36% for the 17–20 / 21–27 / 28–39 / 40+ groups); “at or below” the maximum counts as within. This method was replaced by WHtR on July 7, 2026 — see the archive calculator. Worked examples: male 180 lb + 36 in → 23.07%; female 140 lb + 32 in → 29.39%.
Legacy multi-site tape (pre-June 2024)
Male: %BF = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76 Female: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Formulas quoted verbatim from AR 600-9 Appendix B, Figures B-1 and B-2. Units: all measurements in inches, computed at full precision (log10 = base-ten logarithm). Display: two decimal places, half away from zero; same archived age-group maxima. This method was replaced by the single-site tape in June 2024, then by WHtR — see the archive calculator.
Worked examples: male 70 in / 15 in neck / 36 in abdomen → 21.25%. Female 65 in / 13 in neck / 30 in waist / 40 in hip → 31.09%. Note: some circulated examples show 31.11% for the female case — that figure comes from rounding the intermediate logarithms before multiplying; carried at full precision the formula gives 31.09%, which is what our calculator computes.
Legacy screening tables (pre-July 2026)
The archived height/weight screening calculator performs an exact table lookup against AR 600-9 (2019) Table B-1 — no computation, no interpolation: the maximum screening weight for the entered height, gender, and age group is read directly from the table (male 60–80 in, female 58–80 in; age groups 17–20 / 21–27 / 28–39 / 40+). Heights are rounded to the nearest whole inch. The full tables are printed on the archive page, and the calculator reads its lookup data from those same printed tables, so there is exactly one copy of the data.
Unit converters
inches → cm: cm = inches × 2.54 (exact, by definition) cm → inches: inches = cm ÷ 2.54 feet+in → in: total = feet × 12 + inches pounds → kg: kg = pounds × 0.45359237 (exact; Phase 2 page)
Rounding policy
- WHtR ratio: 3 decimal places, round half away from zero.
- Body-fat estimates: 2 decimal places, round half away from zero.
- Target/buffer waist and max-waist references: nearest ½ inch.
- Height conversions to cm: 1 decimal place.
- Pass/fail-style status comparisons always use the unrounded value (see the comparison rule above).
Input bounds (as implemented)
Values outside these ranges produce a clear corrective message — the calculators never silently clamp or fabricate a result. Blank, non-numeric, zero, and negative inputs are also rejected with explanations.
| Calculator | Input | Accepted range |
|---|---|---|
| WHtR calculator | Height | 3–8 ft (0–11.9 in) or 90–245 cm |
| WHtR calculator | Waist | 20–70 in or 50–180 cm |
| Waist Target / Height-to-Inches | Height | same as WHtR |
| Archived screening | Height | 50–90 in, whole inches; data covers 58–80 (female) / 60–80 (male) |
| Single-site tape | Weight | 80–400 lb |
| Single-site tape | Abdomen | 20–70 in |
| Multi-site tape | Height | 50–90 in |
| Multi-site tape | Neck / Abdomen / Hip | 10–25 / 20–70 / 25–80 in |
| Inches–cm converter | Value | 0–500 (zero valid — it is a pure converter) |
Measurement protocol (brief)
The official Army WHtR measurement is taken at the level of the iliac crest, with the soldier standing, exhaling normally, feet shoulder-width apart. The full self-measurement protocol — including the errors that make home readings differ from official ones — is in the waist measurement guide; height measurement is covered separately.
Known limitations
- Self-reported measurements vary by one to three inches depending on technique.
- Hydration, posture, and time of day affect waist circumference.
- Legacy formulas estimate body fat from circumference ratios; they were never direct measurements.
- No tool on this site replaces an official ABCP assessment.
Independent verification log
Every calculator was tested by driving the real page in a browser (real form interactions, not code inspection) against pre-computed expected values before publication. No human reviewer has independently verified these results; do not infer expert review.
| Date | Calculator | Cases | Method | Result |
|---|---|---|---|---|
| 2026-10-27 | WHtR calculator (homepage) | 12-case matrix: worked examples, metric equivalence, unit-switch preservation, 0.549/0.550/0.550-display boundaries, 5 validation cases | Automated browser testing | PASS |
| 2026-10-27 | Archived screening calculator | 10 cases: all 4 age groups at 70 in, female rows, out-of-range, empty, decimal input, full Table B-1 rendering (21+23 rows) | Automated browser testing | PASS |
| 2026-10-27 | Single-site tape calculator | 8 cases: both worked examples, at-maximum boundary, within/above statuses, empty/negative/zero/out-of-range | Automated browser testing | PASS |
| 2026-10-27 | Multi-site tape calculator | 9 cases: both worked examples, age-group statuses, hip toggle, abdomen≤neck guard, empty/negative/zero | Automated browser testing | PASS |
| 2026-10-27 | Waist Target Calculator | 6 cases: 5’10″/5’4″ targets+buffers, metric equivalence, unit-switch, empty input | Automated browser testing | PASS |
| 2026-10-27 | Height-to-Inches / Inches-to-cm | 13 cases: spec worked examples both directions, metric input, zero, empty/negative | Automated browser testing | PASS |
Change log
2026-10-27 — Initial methodology published, covering the WHtR calculator, the three archived calculators, and the converters as then implemented.
Related
- WHtR calculator — the current standard, with a working estimate
- Single-site tape archive · multi-site tape archive · screening table archive
- Waist Target Calculator · Height to Inches · Inches to cm
- Sources and Accuracy & Limitations — publishing soon