How many calories does lifting weights burn?
A typical hour in the weights room burns somewhere around 200 to 350 kcal. An hour of brisk walking burns about the same. People who have just finished a genuinely hard session tend to find that figure insulting.
It is correct. It is also the least interesting thing about lifting.
The arithmetic
Resistance training sits at roughly 3.5 METs for ordinary gym work and perhaps 5.5 for a dense, breathless session. One MET is about 1 kcal per kilogram of bodyweight per hour, so:
| Bodyweight | Ordinary session, 1 h | Hard session, 1 h | |
|---|---|---|---|
| 55 kg | 120 lb | ~190 kcal | ~300 kcal |
| 70 kg | 155 lb | ~245 kcal | ~385 kcal |
| 85 kg | 185 lb | ~300 kcal | ~465 kcal |
| 100 kg | 220 lb | ~350 kcal | ~550 kcal |
Those are gross figures. A 70 kg (155 lb) person burns about 70 kcal an hour simply existing, so the genuinely extra cost of an ordinary session is closer to 175 kcal — the same gross-versus-net gap that inflates step-count estimates.
Most of a session is not work
Here is why the number is so modest. A hard set of five squats takes about twenty seconds. Twenty sets in an hour is therefore six or seven minutes of actual effort. The remaining fifty-odd minutes go on resting, loading plates, waiting for a rack and looking at your phone — minutes costing barely more than standing up does.
This is not a flaw in how you train. Heavy strength work requires long rests; that is what lets you lift a load worth lifting. Cutting rest to ninety seconds to raise the burn makes you weaker at the thing the session exists for. Circuits and supersets do push the figure up, and they buy it by reducing the load — a reasonable trade for conditioning, a poor one for keeping muscle.
Heart rate is the wrong instrument here
Your pulse during a heavy set has very little to do with the energy that set costs. It rises from blood pressure response, breath-holding, isometric load on a small amount of muscle, and general sympathetic drive. A set of deadlifts can put you at 160 bpm for an energy cost of a few kilocalories.
Wrist trackers convert heart rate into calories using a relationship derived from steady-state cardio, where pulse and effort genuinely move together. Applied to strength work that conversion over-reports, sometimes by a wide margin — which is how a 45-minute session comes back as 600 kcal. The device cannot see load at all, either: the same movement at 20 kg or 100 kg (45 lb or 220 lb) produces identical wrist data. There is more on where the estimate breaks down in how accurate Apple Watch calorie tracking is.
The practical consequence is narrow and important. Do not eat a lifting session back. The figure you would be eating back is the least reliable one your tracker produces.
What lifting is actually for in a deficit
Weight loss is not one quantity. Whatever you lose comes off as some mixture of fat and lean tissue, and the ratio is not fixed — it responds mainly to protein intake and to whether you are giving muscle an ongoing reason to exist. Resistance training is that reason.
The usual argument for this is metabolic, and it is weaker than people claim. Skeletal muscle costs roughly 13 kcal per kilogram per day at rest, about 6 kcal per pound, so holding on to 3 kg (6.6 lb) of it is worth something like 40 kcal a day. Real, but not a headline.
The stronger argument is about what you arrive at. Lose 10 kg (22 lb) with lean mass intact and nearly all of it was fat: you are smaller, your strength is unchanged, your maintenance calories sit close to where they started, and you can still do enough each day to hold the result. Lose the same 10 kg with 3 kg of it from lean tissue and only 7 kg was fat — you shed more total weight for less change in composition, you are weaker, and your maintenance is lower than it needed to be. Repeat that two or three times across a decade and the gap stops being trivial.
Beginners, people coming back after a layoff and people carrying more fat can often go beyond preservation and actually add tissue while losing weight; building muscle in a deficit covers who that applies to.
So is the small number a reason not to lift?
No, and the inversion is the point. A 250 kcal session is a poor way to create a deficit — the day’s burn is mostly not up to you — and a very good way to decide what the deficit removes.
Create the deficit with food, where the leverage is. Lift to steer what comes off. Judged as cardio, an hour of squats is unimpressive. Judged as the thing that determines whether you finish lighter and strong or merely lighter, it has no substitute.
General information, not medical advice.