Calculadora de grasa corporal
Estima tu porcentaje de grasa corporal con el método de cinta métrica de la Marina de EE. UU., además de la masa magra, la masa grasa y tu categoría de forma física.
Cómo 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.
Cómo funciona
Fórmula de grasa corporal de la Marina de EE. UU.
Hombres: %GC = 86,010·log₁₀(cintura − cuello) − 70,041·log₁₀(altura) + 36,76 Mujeres: %GC = 163,205·log₁₀(cintura + cadera − cuello) − 97,684·log₁₀(altura) − 78,387 Masa grasa = peso × %GC Masa magra = peso − masa grasa Todas las circunferencias en pulgadas
El método de la Marina estima la grasa corporal a partir de unas pocas circunferencias y la altura, usando una relación logarítmica. Resta el cuello de la cintura (y suma la cadera en el caso de las mujeres) para aislar la grasa del tronco, y la escala con la altura. Es rápido, no necesita báscula especial y es sorprendentemente fiable para la mayoría de las personas.
Ejemplo resuelto
Un hombre de 180 cm y 90 kg con un cuello de 40 cm y una cintura de 90 cm obtiene alrededor del 20 % de grasa corporal, lo que equivale a unos 18 kg de grasa y 72 kg de masa magra: dentro del rango de forma física aceptable.
Calculadora de grasa corporal: la guía completa
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.
Preguntas frecuentes
¿Es fiable el método de la cinta métrica de la Marina?
Sí, dentro de lo razonable: suele acertar con un margen de unos 3 puntos porcentuales frente al pesaje hidrostático. Es menos preciso en personas muy delgadas o muy corpulentas, pero excelente para seguir la evolución con el tiempo.
¿Cómo debo medir las circunferencias?
Con la cinta ajustada pero sin apretar la piel. El cuello justo bajo la laringe; la cintura a la altura del ombligo en hombres y en el punto más estrecho en mujeres; la cadera en su punto más ancho. Mide siempre igual para comparar bien.
¿Qué porcentaje de grasa corporal es saludable?
Varía por sexo y edad. A grandes rasgos, en hombres un 10–20 % se considera bueno y en mujeres un 18–28 %. Por debajo de esos rangos entra en zona atlética, y muy por debajo puede ser perjudicial para la salud.