Know Your Numbers

BMI is a screening measure, not a diagnosis. It does not account for muscle mass, bone density or body composition — athletes often score “overweight” with low body fat. Use the Body Fat Calculator alongside it, and discuss your results with a healthcare professional.

The Navy method is typically accurate within about ±3–4% compared with clinical scans. Measure your waist horizontally at navel level, neck just below the larynx, and hips (women) at the widest point. For medical-grade body composition, ask a professional about DEXA or hydrostatic testing.

The Devine (1974) and Robinson (1983) formulas were developed for medical dosing and describe a midpoint, not a target. Frame size, muscle mass and personal health matter more than any single figure — treat these numbers as a conversation starter with your doctor, not a verdict.

Pregnancy information disclaimer: Only about 1 in 20 babies arrive on their exact due date — a window of two weeks either side is completely normal. This estimate assumes a regular 28-day cycle and cannot replace dating scans or your midwife's / obstetrician's advice. If you have any concern about your pregnancy, contact your healthcare provider promptly.

Targets use the standard estimate that a 500 kcal daily deficit ≈ 1 lb (0.45 kg) of weight change per week. Real results vary with metabolism, hormones, sleep and adherence. Avoid very low-calorie diets without medical supervision, and never go below the safety floor shown above on your own.

Grams use the standard energy values: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g. Ketogenic and other restrictive diets are not suitable for everyone — including people who are pregnant, have kidney or liver conditions, or take diabetes medication. Check with a registered dietitian before major changes.

Roughly 20% of daily water usually comes from food, and thirst is a reliable guide for most healthy adults. People with kidney or heart conditions may have prescribed fluid limits — follow your clinician's advice over any calculator.

The 220 − age formula is a population average; individual maximums vary by ±10–12 bpm. If you take heart-rate–affecting medication (such as beta blockers), these zones will not apply — ask your clinician for personal targets, and stop exercising if you feel chest pain, severe breathlessness or dizziness.

Race predictions use the Riegel formula, which assumes you've trained appropriately for the longer distance. Hills, heat, course crowding and fueling all move real finish times — treat predictions as a planning guide, not a promise.

Suggestions include about 15 minutes to fall asleep, and the 6- and 5-cycle options (9 and 7.5 hours) suit most adults, who generally need 7–9 hours. Persistent insomnia, loud snoring or daytime sleepiness are worth discussing with a sleep professional.