CALORIE, PROTEIN AND FIBER CALCUALTOR.
Three numbers, one form. Tell it your height, weight, age and roughly what your week actually looks like, and you’ll get a daily calorie target, a protein target and a fibre target. Takes about twenty seconds, and you don’t have to hand over your email to see the result.
It's important to tealise thatevery calculator is an estimate. The equation behind this one is the one used in the research, and it’s a good one, but it’s working from averages. Your real maintenance could sit a couple of hundred calories either side of what it says. The number below is a starting point, not a definitive, what actually tells you the truth is what the scale does over the next two or three weeks.
WHAT TO DO WITH THESE NUMBERS
Calories. Eat roughly that, most days, and check your weight trend over a fortnight rather than day to day. Weight bounces around with salt, carbs, training and sleep, a single morning tells you nothing. If the trend hasn’t moved in two weeks, take 100–150 off and look again.
Protein. This is the one most people are furthest off, and the one that does the most work. It keeps you full, and it’s what protects your muscle while you’re losing fat so you end up looking like you’ve lost weight rather than just become a smaller version of the same shape. Spread it across the day rather than trying to cram it into dinner.
Fibre. The UK guideline is 30g and the average adult manages about 20g. It’s not glamorous, but it’s most of the difference between a diet that feels manageable and one that leaves you hungry at 9pm. Fruit, veg, beans, lentils, oats, wholegrains.
WHY YOUR NUMBER MIGHT BE OFF
The single biggest source of error is the activity question. Almost everyone picks one level too high — training four times a week doesn’t make you “very active” if the other 100 waking hours are spent at a desk and in the car. If you’re between two options, take the lower one. You can always eat more later; it’s much more demoralising to go the other way.
Your watch isn’t a better answer either. Wearables are reasonable at steps and poor at calorie burn — they routinely overestimate by 20–30%, and they don’t know your resting metabolism.
COMMON QUESTIONS
HOW MANY CALORIES DO I NEED TO LOSE WEIGHT?
Around 15–20% below your maintenance for most people, which is what the calculator gives you. That’s roughly 0.5–1% of bodyweight a week. Faster than that and you lose more muscle, feel worse, and are more likely to pack it in.
HOW MUCH PROTEIN SHOULD I EAT EVERYDAY?
Between 1.6 and 2.2g per kg of bodyweight, towards the top end when you’re in a deficit. For most people that’s noticeably more than they’re currently eating.
Is 30g of fibre a day realistic?
Yes, but not overnight. If you’re on 15g, going straight to 30 will make you uncomfortable. Add 5g a week and drink more water alongside it.
SHOULD I EAT BACK BURNED CALORIES?
No. The target already accounts for your training — that’s what the activity question was for. Eating them back a second time is the most common reason people stall.
WHAT IF I'M ON WEIGHT LOSS JABS?
The calorie number still applies, but hitting protein on a suppressed appetite is a different problem, and protecting muscle matters more when the weight is coming off quickly.