Carbohydrate Calculator

Eight activity levels, and why that is not better

Open the activity dropdown on this tool and it offers eight choices, more than any other calculator on this site. Sedentary. Easy exercise, 2 to 3 times a week. Moderate, 4 times. Active, 5 times. Very active, 5 times intense. Day by day. Day by day intense or twice daily. Daily exercise plus a physical job.

That looks like precision, and it is worth being straight with you: it is not.

Underneath those labels sit multipliers of 1.2, 1.375, 1.4187, 1.4625, 1.54999, 1.63765, 1.7252 and 1.91. Look at them for a moment. One point four one eight seven. One point five four nine nine nine.

Those numbers are quoted to five decimal places, which implies somebody knows your energy expenditure to within about one part in ten thousand. Nobody does. The activity multiplier is the single roughest component of the whole calculation, an estimate with a real-world error of ten or twenty percent in either direction, and our TDEE Calculator explains why the gap it is trying to bridge is genuinely unknowable from a dropdown. Attaching four extra decimals to a guess does not sharpen it. It just dresses it up.

The practical upshot: do not agonise over the choice between "moderate, 4 times" and "active, 5 times". The difference between them is about 3 percent, which is comfortably inside the noise. Pick the one that honestly describes your week, treat the answer as a starting point, and adjust based on what actually happens to you over the following month. That is the only calibration that has ever worked.

The useful bit: carbs per meal

Now the thing this tool has that its siblings do not, and the reason to use it.

It asks how many meals you eat a day, and then divides your carbohydrate across them. That sounds trivial. It is the most practically useful output on the page, because nobody has ever eaten a daily total. You eat meals.

Take a 30 year old woman, 165 cm, 65 kg, exercising 4 times a week, eating 3 meals a day, at 50 percent carbohydrate. Her resting burn is about 1,370 calories and her daily total lands near 1,944. So:

Look at the difference in usefulness between those last two columns. "Eat 243 g of carbohydrate today" is a number you cannot act on until bedtime, by which point it is too late to do anything about it. "Eat about 81 g of carbohydrate at this meal" is something you can hold in your head while looking at a plate. Roughly a cup of cooked rice and a piece of fruit. That you can actually do.

Three rows, and the floor underneath them

The tool gives you three scenarios rather than making you choose one: maintain, lose, and gain. The loss and gain rows are a modest 250 calories either side of your maintenance, which works out at roughly a quarter of a kilogram a week in either direction.

That is a deliberately gentle adjustment and we would defend it. Our Calorie Deficit Calculator goes into why patient beats aggressive, but the short version is that a small deficit is easier to live with, costs you less muscle, and is far more likely to still be happening in March.

There is also a floor. If the weight-loss row would take you below 1,500 calories as a man or 1,200 as a woman, the tool holds there rather than going lower. You will not usually meet it on a 250 calorie cut, but it is there.

Where the per-meal figure earns its keep

Splitting carbohydrate evenly across your meals is a sensible default, and it is what this tool does. But once you have the per-meal number, the interesting move is to distribute it unevenly on purpose.

Carbohydrate is the fuel for hard work. It gets stored as glycogen in your muscles and liver, and glycogen is what powers anything above an easy effort. So the meals surrounding your training session are the ones where carbohydrate has an actual job to do: topping the tank up beforehand, and refilling it afterwards. The meal on a rest-day afternoon spent at a desk has no such job.

Our example's 81 g per meal is an average, not a rule. If she trains in the evening, putting 110 g into lunch and dinner and 40 into breakfast serves her better than three identical 81 g meals, even though the day totals the same. The tool cannot know when you train, so it divides evenly and leaves the shaping to you.

One thing worth saying, since this tool splits only carbohydrate: protein is the macro that genuinely wants even distribution across the day, because your body cannot bank it. Our Protein Intake Calculator covers the per-meal figure for that. Carbohydrate is the one you are allowed to move around.

Questions people ask

There are eight activity levels. Which is mine?

Whichever honestly describes your typical week, and do not lose sleep over adjacent options. The gap between neighbouring choices is a few percent, which is smaller than the error in the estimate itself.

Does the number of meals change my total?

No. It only changes how the total is divided up. Three meals or six, your daily carbohydrate is identical. Meal frequency does not affect weight change.

What carbohydrate percentage should I use?

Between 45 and 65 percent sits inside official guidance, and 50 to 60 suits most people who train. Our Carb Calculator goes into how much carbohydrate you actually need, which is a more interesting question than it sounds.

Why is one of the multipliers 1.54999?

An excellent question, and the honest answer is that it should be 1.55. We have flagged it. It makes no practical difference to your result, but you spotted it, and we would rather say so than pretend it was intentional.

References

Where the figures come from. The resting equation this tool runs is Mifflin-St Jeor, published in the American Journal of Clinical Nutrition, and the systematic review finding it the most accurate of the common resting equations is Frankenfield and colleagues. The Acceptable Macronutrient Distribution Range for carbohydrate of 45 to 65 percent of energy is from the Institute of Medicine's Dietary Reference Intakes.

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241-247. https://doi.org/10.1093/ajcn/51.2.241
2. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775-789. https://doi.org/10.1016/j.jada.2005.02.005
3. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy. Washington DC: The National Academies Press. https://www.ncbi.nlm.nih.gov/books/NBK591020/