Calculadora de gordura corporal
Estime o seu percentual de gordura corporal com o método da fita métrica da Marinha dos EUA, além da massa magra, massa gorda e a sua categoria de aptidão física.
Como usar esta calculadora
- 1Measure first thing in the morning, before eating, with the tape snug but not compressing the skin.
- 2Measure your neck just below the larynx, letting the tape slope slightly downward at the front.
- 3Measure your waist at the navel if you are male, or at the narrowest point if you are female.
- 4If you are female, also measure your hips at their widest point.
- 5Take each measurement three times and use the average.
Como funciona
Fórmula de gordura corporal da Marinha dos EUA
Homens: %GC = 86,010·log₁₀(cintura − pescoço) − 70,041·log₁₀(altura) + 36,76 Mulheres: %GC = 163,205·log₁₀(cintura + quadril − pescoço) − 97,684·log₁₀(altura) − 78,387 Massa gorda = peso × %GC Massa magra = peso − massa gorda Todas as circunferências em polegadas
O método da Marinha estima a gordura corporal a partir de algumas circunferências e da altura, usando uma relação logarítmica. Subtrai o pescoço da cintura (e soma o quadril no caso das mulheres) para isolar a gordura do tronco e a ajusta pela altura. É rápido, dispensa balança especial e é surpreendentemente confiável para a maioria das pessoas.
Exemplo resolvido
Um homem de 180 cm e 90 kg, com pescoço de 40 cm e cintura de 90 cm, obtém cerca de 20 % de gordura corporal, o que equivale a aproximadamente 18 kg de gordura e 72 kg de massa magra: dentro da faixa de aptidão aceitável.
Calculadora de gordura corporal: o guia completo
Why body fat percentage beats BMI
BMI only knows your height and weight, so it cannot tell muscle from fat. A muscular athlete and a sedentary person of the same height and weight get the same BMI despite completely different body composition — which is exactly why the armed forces adopted a tape test as a secondary screen.
Body fat percentage answers the question BMI is really being used as a proxy for: how much of your mass is fat tissue. It also gives you lean body mass, which is the number that matters for protein targets, drug dosing, and tracking whether a diet is costing you muscle.
What the categories mean
Essential fat — around 3–5% for men and 10–13% for women — is the minimum needed for hormone production, nerve insulation, and organ protection. Below it, health consequences follow quickly, and for women menstrual function is usually the first thing to go.
The athletic and fitness bands describe people who train consistently. Average describes most of the adult population and is not itself a health problem. The obese band is where metabolic risk starts to rise sharply, particularly when the fat is carried around the abdomen rather than the hips and thighs.
Bands shift with age. Body fat naturally rises a few points per decade as lean mass declines, and a percentage that would be high at 25 is unremarkable at 55.
Measuring accurately
Tape technique is the largest source of error in this method — far larger than the formula itself. Use a flexible non-stretch tape, keep it horizontal and parallel to the floor, and pull it snug enough to sit against the skin without indenting it. Measure at the end of a normal exhale, never while holding your breath or sucking in.
Consistency matters more than absolute accuracy when tracking change. Measure at the same time of day, in the same conditions, and take three readings at each site to average. A single measurement's worth of noise can easily be a full percentage point of apparent body fat.
How this compares to other methods
DEXA scanning is the practical gold standard, accurate to about 1–2 percentage points and able to report where the fat sits. Hydrostatic weighing is similarly accurate but awkward. Both need a clinic appointment.
Bioelectrical impedance scales are convenient but highly sensitive to hydration — the same person can read three points apart morning and evening. Skinfold calipers are accurate in trained hands and unreliable otherwise. The Navy tape method sits in a useful middle ground: free, repeatable, and typically within about three points of DEXA.
Perguntas frequentes
O método da fita da Marinha é confiável?
Sim, dentro do razoável: costuma acertar com margem de cerca de 3 pontos percentuais em relação à pesagem hidrostática. É menos preciso em pessoas muito magras ou muito corpulentas, mas excelente para acompanhar a evolução ao longo do tempo.
Como devo medir as circunferências?
Com a fita ajustada, mas sem apertar a pele. O pescoço logo abaixo da laringe; a cintura na altura do umbigo nos homens e no ponto mais estreito nas mulheres; o quadril no ponto mais largo. Meça sempre da mesma forma para comparar bem.
Que percentual de gordura corporal é saudável?
Varia por sexo e idade. De modo geral, 10–20 % é bom em homens e 18–28 % em mulheres. Abaixo disso entra-se na faixa atlética, e muito abaixo pode ser prejudicial à saúde.