Log your skinfolds. Watch the trend. Ignore the noise. Your data stays in your browser.
This tracker uses the Jackson-Pollock 3-site and 7-site protocols to estimate body fat percentage from skinfold thickness measurements. You enter measurements in millimeters for each site, select your protocol (3-site for quick checks, 7-site for more accuracy), and the tool calculates body density using the Siri equation, then converts to body fat percentage. The 3-site protocol uses chest, abdomen, and thigh for men; triceps, suprailiac, and thigh for women. The 7-site adds midaxillary and subscapular for a more complete picture. All entries are saved locally with timestamps so you can track trends over weeks and months.
Tip: Self-measurement error is typically ±8%. For best results, have a trained partner measure for you, or practice the pinching technique until your readings stabilize within 1-2mm across three attempts.
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⚠️ Technician Error Warning: Self-measurement error is typically ±8%. A skilled technician achieves ±3-5%. Track trends, not absolutes.
Convert your skinfolds to body fat percentage instantly.
See your lean mass from skinfold-derived body fat.
Set goals based on your skinfold trends.
Pinch the skin and subcutaneous fat away from the muscle, hold the caliper perpendicular to the fold, and read the measurement 1-2 seconds after releasing the trigger.
You can, but self-measurement error is typically ±8%. A trained partner or technician achieves ±3-5%. For best results, practice until readings stabilize within 1-2mm across three attempts.
Use 3-site for quick weekly checks. Use 7-site for more accurate monthly assessments. The 7-site adds midaxillary and subscapular measurements for a fuller picture.
Hydration, meal timing, and menstrual cycle affect skinfold thickness. Always measure at the same time under the same conditions. Track trends over weeks, not days.