How to calculate your body fat percentage

The scale is lying to you

You weigh 82 kilos. Fine. And what does that mean? Well, it depends. A person of 82 kilos with 15% body fat has an athletic physique. Another person of 82 kilos with 35% body fat has a health problem. The number on the scale tells you nothing on its own, because it doesn't distinguish between muscle, fat, water and bone.

What really matters is your body composition. How much of what you weigh is muscle and how much is fat. That figure does change things: it tells you where you are and where you're heading.

4 ways to measure your body fat

The mirror. Free and more useful than it sounds. Search Google for "body fat percentage visual guide" and compare. It's not exact, but it gives you a fairly good idea. To get started, it's plenty.

The caliper. It's a small device that measures skin folds at different points on the body, it costs 10 or 15 euros, and with a bit of practice it's reasonably reliable. Ask someone at the gym to show you the first time.

The bioimpedance scale. Those "smart" scales that send an electrical current through your body. They're convenient, but the result changes a lot depending on how much you've drunk, what you've eaten or the time of day. Use it always at the same hour to see trends, not exact values. Measured against the reference method in healthy adults who were neither athletes nor pregnant, the error margin for a single person is so wide that one isolated reading tells you nothing.

The DEXA scan. This is the genuinely good method. A full-body scan that measures fat, muscle and bone by area. It costs between 60 and 100 euros at private clinics. If you're serious, it's worth doing once a year.

Normal ranges by age and gender

For men aged 20 to 39, between 8% and 20% is healthy. Below 8% we are talking about competition level. Above 25% the risks start.

For men aged 40 to 59, between 11% and 22% is normal.

For women aged 20 to 39, between 21% and 33% is fine. Below 16% it can affect hormones and the menstrual cycle. Above 35% there is risk.

For women aged 40 to 59, between 23% and 34% is healthy.

These numbers are approximate and there is no universal cut-off. When body fat was measured in white, African American and Asian adults using reference methods, what set the healthy range was sex, age and ethnic background, not one figure for everybody. What matters is not the exact number but the direction. Are you going down? Are you going up? Are you stable? That's what counts.

How to use this figure to set a real goal

If your body fat percentage is above the healthy range, the path is clear: eat a little less than you spend and train for strength. If you're within the range, you can focus on gaining muscle or improving your performance.

Here is something that may catch you off guard if you are just starting out: you can lose fat and gain muscle at the same time. It's called body recomposition, it is most common while you are still new to training, and the literature on people who already train for strength shows it happens to them too. The scale can sit still for weeks while your body quietly changes underneath it, and other people tend to notice before you do.

Do not obsess over the number

Measure yourself every 4 or 6 weeks, always under the same conditions, and note the trend rather than the isolated figure. A 22% that drops to 20% in two months is real progress, whatever the scale says. Use the figure as a compass that guides you, not as a judge that punishes you.

Knowing your number is one thing, lowering it slowly is another: Losing fat without rushing: why going slowly is the fast way not to put it back on.

And if you need someone to help you interpret the numbers, come by Gym Triple X and we'll talk. That's what we're here for.

All of this works if you apply it. And if you know you won't apply it on your own, being clear about that is already progress: there is a personal trainer on the Costa del Sol for exactly that moment. Honesty with yourself is worth more than another perfect plan saved on your phone.