Your treadmill's "calories burned" number is probably wrong — and not by a little. Research on calorie-tracking accuracy has found overestimates ranging from roughly 20% up to over 100 calories per session, depending on the machine and how it's calibrated. That number on the screen isn't a measurement. It's a guess wearing a lab coat.
Where the number actually comes from
A treadmill doesn't know your body. It doesn't know your muscle mass, your metabolic rate, or how efficiently you move. What it has is your weight (if you bothered to enter it), your speed, and an incline setting — and from that, it runs a generic formula based on population averages called METs (metabolic equivalents).
The problem: METs were never built for machines that let you cheat the movement. If you're holding the handrails — even lightly, even without realizing it — you're offloading real work onto your arms while the machine keeps counting as if your legs did it all.
A 2005 study published in the Journal of Applied Physiology found that MET-based calorie estimates can overestimate actual energy expenditure by up to 20%, because a single fixed formula doesn't account for individual differences in efficiency and body composition.
It's not just treadmills
Cardio machines across the board have this problem. A widely cited 2018 comparison of gym cardio equipment found some machines — ellipticals in particular — overestimating calorie burn by as much as 130 calories over a 30-minute session. Independent researchers and trainers who've dug into consumer cardio equipment generally land on the same range: expect somewhere between 10% and 15% inflation as a baseline, sometimes far more.
Why the machine has no incentive to be honest
Nobody's shopping for a treadmill based on which one estimates calories most conservatively. A bigger number on the screen feels like a better workout — it's the same reason a scoreboard always favors optimism. The machine isn't lying to sabotage you. It's just not built to be accurate, and there's no market pressure pushing it to be.
The result is that a lot of people build their entire sense of "how hard did I train today" around a number that was never trustworthy in the first place.
What to trust instead
If you want an honest read on effort, the machine's screen isn't it. Heart rate, perceived exertion, and whether you can hold a conversation are far better signals than a calorie estimate built on a formula that doesn't know who you are.
Better yet — train in a way where the effort is undeniable and doesn't need a screen to validate it. Jump rope doesn't offer you handrails to lean on or an incline setting to game. Every jump is force you generated yourself, landed yourself, and felt yourself. There's no inflated number standing between you and knowing exactly how hard you worked.
You don't need a machine telling you a number you can't verify. You need work you can actually feel.
Source: MET-based calorie estimation error findings via the 2005 study "Metabolic equivalent: one size does not fit all" (Byrne, Hills, Hunter, Weinsier & Schutz), Journal of Applied Physiology, as reported by Garage Gym Reviews. Elliptical/cardio machine overestimation figures and general accuracy consensus via Marathon Handbook.
Elliptical instead of treadmill? Same problem. Here's how far off its calorie counter actually is.
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