Exercise & Training Calculators

Training numbers you can actually compare

Exercise generates numbers faster than almost anything else you do: paces, watts, splits, heart rates, rep counts, calorie readouts. The trouble is that most of them come from different machines, different formulas and different conventions, so they refuse to line up. A rower credits calories one way, an air bike another; one running app quotes minutes per mile, another minutes per kilometre; the gym's heart-rate chart assumes a formula published in 1971. The calculators on this shelf exist to make those numbers comparable, and every one of them shows the formula it used, so you can see exactly where the answer came from.

Broadly, the eight tools here answer three kinds of question. How hard should I be working, which is heart-rate and pacing territory. How much did that session cost me, which is calorie estimation. And how strong am I really, which is what a one-rep max estimate settles. Each section below takes one of those in turn.

Intensity: heart rate and pace

Finding your training heart rate

The Target Heart Rate Calculator starts from an estimate of your maximum heart rate and works down to the beats-per-minute range you should hold at a chosen intensity. It offers two published formulas for the maximum: the classic Fox formula, 220 minus age, and the Tanaka formula, 208 minus 0.7 times age. The two agree exactly at age 40 and diverge either side of it; at 20 Fox gives 200 bpm against Tanaka's 194, and at 60 the order flips, 160 against 166. If you know your resting heart rate, measured first thing in the morning, the calculator switches to the Karvonen method, published by the Finnish physiologist Martti Karvonen in 1957, which works from your heart-rate reserve rather than age alone and so accounts for your own fitness. You also get the five standard training zones in bpm, plus 10-second counts for checking your pulse mid-session without a watch.

Pace, time and distance

The Pace Calculator handles the arithmetic every runner eventually does on their fingers: given any two of pace, time and distance, it works out the third, in kilometres or miles, with your speed alongside. It also projects your finish time at that pace across common race distances. One honest caveat the page itself makes: those projections assume perfectly even pacing, which becomes less realistic as the distance stretches. A 5K projection is a fair target; a marathon projection from a short run is an optimistic ceiling, not a prediction, because real races slow as fatigue builds.

Calorie burn: what a session actually costs

Calorie estimates are where exercise numbers mislead people most, usually because a machine or an app quotes a figure without saying what it measured. Four tools here attack the problem from different angles.

The general-purpose option is the Calorie Burn Calculator by Activity. Pick an activity, set your weight and duration, and it applies the standard formula from exercise physiology: calories burned equals MET times 3.5 times weight in kilograms, divided by 200, times minutes. The MET values come from the 2011 Compendium of Physical Activities, the same reference exercise scientists use. Crucially, it shows gross and net burn side by side. Gross is everything you spent during the activity; net subtracts roughly 1 MET, the cost of simply existing for that time, to show what the exercise itself added. Most fitness trackers quote gross, which flatters the workout.

If your training is measured in distance rather than time, the Miles to Calories Converter turns walking, running or cycling mileage into an estimated burn from your body weight, again with gross and net figures side by side. It is the quicker tool when you know how far you went but not exactly how long it took.

Machine calories are their own dialect

Gym machines complicate things further, because their monitors calculate calories from mechanical work at the flywheel, not from your physiology. The Rowing Calorie Chart takes your Concept2 split or watts, converts between the two using Concept2's own published formulas, and puts the monitor's calorie figure next to a weight-adjusted estimate of what you actually burned, with the gap explained. A 60 kg rower and a 100 kg rower holding the same split see the same monitor number but do not burn the same energy.

The Assault Bike Calorie Chart does the equivalent job for air bikes: watts and time in, a machine-style calorie estimate and a separate physiological one out, plus a printable watts-by-duration chart for the gym wall. And when a workout prescribes calories without naming the machine, the CrossFit Calorie Converter translates a calorie count between Concept2 rowers, air bikes and ski ergs using published coaching ranges. Air bike calories commonly run at 70 to 80 per cent of rower calories for the same effort; the converter gives you the range rather than pretending a single exact number exists, because that convention is a coaching rule of thumb, not a physical constant.

Strength: estimating your one-rep max

Testing a true one-rep max is risky and disruptive to training, so nearly every programme works from an estimate instead. The One Rep Max Calculator takes any weight and rep count and runs it through four proven formulas: Epley as the headline figure, with Brzycki, Lombardi and O'Conner compared alongside. The formulas track each other closely between roughly 2 and 10 reps and drift apart beyond that, so a 5-rep set gives a far more trustworthy estimate than a 15-rep one. The calculator also converts your estimated max into a table of training percentages, which is the number a programme actually asks for; "5 sets of 5 at 82.5 kg" is usable on the gym floor in a way "71 per cent of your estimated max" is not. If a number genuinely matters, for a testing day or a competition opener, averaging all four formulas tends to cancel out each one's individual bias.

How the tools fit together

A realistic week of training touches several of these at once. You might set your steady-run heart-rate ceiling with the Target Heart Rate Calculator, check your interval splits with the Pace Calculator, log the session's true cost through the Calorie Burn Calculator, and set next month's squat loads from the One Rep Max Calculator. The calorie figures feed naturally into the diet-side tools on the Calories & Nutrition shelf; your net burn from exercise is exactly the number a calorie deficit plan wants, and your BMR is the baseline it sits on. Every calculator here is free, and each one prints its working, so when two numbers disagree you can see why rather than guessing.

Common mistakes worth avoiding

• Treating a machine's calorie readout as your personal burn. Monitors measure flywheel work; your body weight changes the physiological cost substantially.
• Eating back gross calories. If you subtract nothing for the sitting-still baseline, you credit yourself energy you would have spent anyway.
• Estimating a one-rep max from a very high-rep set. Past about 10 reps all four formulas are extrapolating well beyond their reliable range.
• Projecting a marathon time from a 5K pace. Even-pace projections ignore fatigue, and the error grows with distance.

Frequently asked questions

Why do the rower and the air bike give different calories for the same effort?

Each manufacturer converts mechanical work to calories with its own assumptions, and the machines load the body differently. That is why the CrossFit Calorie Converter deals in ranges: the commonly coached conversion puts air bike calories at 70 to 80 per cent of rower calories for matched effort.

Which max heart rate formula should I use?

Tanaka (208 minus 0.7 times age) was built from a much larger evidence base than the older 220-minus-age rule and generally tracks measured maximums better, especially away from age 40. Better still, if you know your resting heart rate, use the Karvonen option in the Target Heart Rate Calculator, since it personalises the zones to your fitness.

Are calorie burn estimates accurate enough to plan a diet around?

They are estimates built from population averages, so treat them as a starting point. Use the net figure from the Calorie Burn Calculator or the Miles to Calories Converter, watch your actual weight trend for three or four weeks, then adjust. The trend is the truth; the calculator gets you a sensible first guess.

Is an estimated one-rep max safe to attempt?

An estimate tells you roughly where your max sits; it is not a guarantee you can lift it today. Programme from the percentages rather than testing the single, and if you do test, work up in stages with a spotter.