You press the Units button on a Concept2 monitor and the split box, which was showing 2:05, now says 948. Or a workout on the whiteboard says "30 cal row" and you have no idea what split that means or how long it will take. Either way you have run into split/cal: the same effort expressed in calories per hour instead of time per 500 m.

This guide explains exactly what the number is, how the monitor calculates it, how to convert between cal/hr and a 500 m split, and why the calorie figure on the screen is not the number of calories you actually burned.

What the monitor is showing

The Concept2 Performance Monitor (PM5, and the older PM3 and PM4) can display your pace in three units, and the Units button cycles between them:

Display What it means
/500m Time to cover 500 m at your current pace. The standard rowing split.
watts Your current power output.
cal/hr Calories per hour at your current pace.

All three describe the same stroke. A 2:00 split is 203 watts is 997 cal/hr. Nothing about your effort changes when you press the button; only the unit does.

So "split/cal", "split cal" or "erg cal" is simply your split shown in calories per hour. When the monitor is in calorie mode the distance field changes too: instead of metres rowed it shows total calories, which is what a "30 cal row" counts down.

How the monitor turns a split into calories

The monitor does not measure calories. It measures the flywheel, calculates watts from that, and then converts watts to calories per hour with a fixed formula that Concept2 publishes:

cal/hr = (watts × 4 × 0.8604) + 300

Each part of that has a reason:

  • × 4 assumes the human body is about 25% efficient at turning food energy into work on the handle. For every unit of energy that reaches the flywheel, you burned roughly four.
  • × 0.8604 converts the result from kilojoules to kilocalories (a calorie on the monitor is a kilocalorie, the same unit as food labels).
  • + 300 is a fixed allowance for the energy you would burn in an hour just being alive and moving on the machine, set for a 175 lb (79.5 kg) person.

And watts, in turn, come from the split:

watts = 2.80 ÷ (split in seconds ÷ 500)³

Chain those two together and every split has a cal/hr value, which is what the table below shows.

Split to cal/hr conversion table

Split /500m Watts Cal/hr Cal/min 20 cal takes 50 cal takes
2:30 104 W 657 10.9 1:50 4:34
2:20 128 W 739 12.3 1:37 4:04
2:10 159 W 848 14.1 1:25 3:32
2:05 179 W 917 15.3 1:19 3:16
2:00 203 W 997 16.6 1:12 3:01
1:55 230 W 1092 18.2 1:06 2:45
1:50 263 W 1205 20.1 1:00 2:29
1:45 302 W 1341 22.3 0:54 2:14
1:40 350 W 1505 25.1 0:48 2:00
1:35 408 W 1705 28.4 0:42 1:46
1:30 480 W 1952 32.5 0:37 1:32

Going the other way, if a workout gives you a cal/hr target:

Cal/hr Watts Split /500m
800 145 W 2:14
1000 203 W 2:00
1200 262 W 1:50
1500 349 W 1:40

A useful anchor: 1000 cal/hr is almost exactly a 2:00 split. If you know roughly what a 2:00 feels like, you know what 1000 cal/hr feels like.

The erg split calculator gives you the watts for any split; add the formula above and you have the calories.

Why cal/hr flatters slow rowing

Look at the 2:30 row in the table. Of the 657 cal/hr showing on the monitor, 300 is the fixed allowance and only 357 came from the work you did. At a 1:30 split, 300 of 1952 is the allowance and 1652 is work. The base allowance is almost half the number when you row gently and barely a sixth of it when you row hard.

That has two practical consequences.

Calorie workouts reward power more than metre workouts do. Dropping from a 2:00 split to a 1:35 split makes a 500 m row 21% faster (2:00 becomes 1:35). It makes a 50 cal row 41% faster (3:01 becomes 1:46). Metres scale with the cube root of power; calories scale almost linearly with it. If you are a big, powerful rower, a calorie row is kinder to you than the equivalent distance. If you are a lightweight, it is harsher.

A slow row still shows a respectable calorie number. This is why people are often surprised that a gentle 30-minute paddle "burned" 350 calories. It did not, necessarily. It showed 350 because the monitor added 150 calories of baseline for the half hour whether you were a 60 kg woman or a 100 kg man.

Why it is not the calories you burned

The 300 cal/hr allowance is set for a 175 lb person and the monitor has no idea what you weigh. Concept2 publishes a correction so you can fix it yourself:

true cal/hr = monitor cal/hr − 300 + (1.714 × bodyweight in lb)

Here is what a 2:00 split (997 cal/hr on the screen) works out to at different weights:

Bodyweight True cal/hr at a 2:00 split
130 lb / 59 kg 920
150 lb / 68 kg 954
175 lb / 79 kg 997 (what the monitor shows)
200 lb / 91 kg 1040
220 lb / 100 kg 1074

Two things to notice. The correction is small compared with the effect of the split itself, so the monitor number is a reasonable guide to relative effort even if the absolute figure is off. And the 25% efficiency assumption is also an average; well-trained rowers are a little more efficient and novices a little less, which the monitor cannot see either.

Use the correction from your workout summary cal/hr, not the figure on the last stroke, since the summary is the average for the whole piece.

Should you train by split or by calories?

For rowing, use the split. Every benchmark, every ranking and every training plan in the sport is written in time per 500 m. A 2K is 2000 m, not 133 calories. The split is also the more sensitive number: a change from 2:00 to 1:58 is visible immediately, while the same change moves cal/hr from 997 to 1034, which is harder to hold in your head mid-piece.

For mixed workouts, calories are fine, with two cautions. First, Concept2 uses the same formula on the RowErg, SkiErg and BikeErg, so calories are roughly comparable across those three. They are not comparable with any other brand's machine; an air bike's "calorie" is a different calculation entirely. Second, remember the scaling above: a 50 cal row and a 500 m row are not interchangeable, and which one is harder depends on who is rowing.

If you want to know what split to hold for a calorie target, work backwards from the table: a 20 cal row in about a minute needs a 1:50 split, and a 50 cal row in two minutes needs a 1:40.

Common questions

How do I change the rowing machine from cal to split?

On a PM5, press the Units button (bottom row of buttons, or Change Units on the Just Row screen) to cycle between /500m, watts and cal/hr. The monitor remembers the setting for the session. On a PM3 or PM4 the button is labelled Units as well.

How many calories does a 2K burn?

At a 2:00 split (an 8:00 2K) the monitor shows about 133 calories. Correct it for your bodyweight with the formula above: roughly 123 for a 130 lb rower and 143 for a 220 lb rower. A 500 m at the same pace shows about 33 calories.

What is a good cal/hr on a rowing machine?

The same answer as for a good split: it depends on who you are and how long you are rowing for. As a rough guide, 1000 cal/hr is a 2:00 split, which is a solid recreational pace held over a 2K. Our rowing split benchmarks page explains how to judge a split against distance, bodyweight and the ranking data, and the same judgement applies to the calorie figure.

Is 1000 cal/hr a 2:00 split?

Yes, almost exactly: 1000 cal/hr is 203 watts, which is a 1:59.8 split. It is the most useful conversion to memorise.

Why does the calorie count go up faster when I row hard?

Because calories are nearly proportional to watts, and watts rise with the cube of your speed. Rowing 10% faster takes about 33% more power and shows about 25% more calories per hour, the exact figure depending on where you started.

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