Concept2 watts and split explained
On a Concept2 erg your “split” is the time it would take to cover 500 m at your current power, and the monitor can show that same effort as watts. The two are tied together by a single cube-law formula. Here is what the split means, how watts are derived from it, a worked example, and the one thing the number does not tell you — your speed on the water.
Open the Rowing Split calculatorWant to flip between pace and power instantly? The Rowing Split calculator applies the exact formula below, so you can type a split and read the watts, or the other way round.
What a “split” is
A split on a Concept2 ergometer is the time it would take to row 500 m at your
current rate of work, written as minutes and seconds — for example 2:00 /500m.
It is a pace, not a distance: even in a 2000 m piece, the monitor is constantly asking “at
this instant, how long would 500 m take?” The reason rowers pace in splits is that the
distance is fixed and familiar, so a 500 m split reads like a lap time.
The erg does not measure force on the water. It measures the work you do spinning a flywheel against air resistance, then converts that work into power in watts and, from power, into the equivalent 500 m pace. Split and watts are therefore two views of the same underlying number.
The watts formula, both ways
Concept2 publishes a fixed relationship between the pace shown on the monitor and the power in watts. Writing the split as seconds per 500 m, the power is:
And, solving the same relationship for the split when you know the power:
- watts
- average power output on the flywheel
- split_sec_per_500
- the 500 m pace expressed entirely in seconds (so 2:00 = 120)
- 2.80
- the Concept2 constant relating pace to power on its ergometers
- the cube
- power rises with the cube of speed, so small pace gains cost large power
Worked example: 2:00 /500m
Take a steady 2:00 /500m split and find the watts.
- Convert the split to seconds:
2:00 = 120 s. - Speed term:
120 / 500 = 0.24. - Cube it:
0.24³ = 0.013824. - Divide the constant:
2.80 / 0.013824 = 202.5. - Result: a 2:00 split is about 203 watts.
Running it the other way, 203 W gives 500 × (2.80 / 203)^(1/3) ≈ 120 s, i.e.
2:00 — the two forms are consistent.
Common splits and their watts
Because power depends on the cube of pace, the watts column climbs steeply as the split drops. Each 10-second improvement near 2:00 is worth far more power than the same 10 seconds near 2:30.
| Split /500m | Seconds | Watts (approx.) |
|---|---|---|
| 1:30 | 90 | 480 W |
| 1:40 | 100 | 350 W |
| 1:50 | 110 | 263 W |
| 2:00 | 120 | 203 W |
| 2:10 | 130 | 159 W |
| 2:20 | 140 | 128 W |
| 2:30 | 150 | 104 W |
Notice the pattern: moving from 2:00 to 1:50 adds roughly 60 W, but from 2:30 to 2:20 adds only about 24 W. That is the cube law in practice — the faster you already are, the more power a further gain demands.
Why the 2.80 constant is erg-specific
The constant comes from Concept2’s flywheel work model: it fits the power you put into the machine’s spinning wheel to the pace the monitor displays. That model is a property of the ergometer, not of a boat moving through water. There is no hull, no drag from a wetted surface, no crew shifting the shell’s speed within each stroke, and no wind.
So a 2:00 erg split is not a 2:00 on the water. On the water, the same power moves different boats at very different speeds: a light single scull and a heavy eight, calm water and a headwind, good rigging and bad, all change the distance that a given wattage produces. The erg tells you how hard you are working; the water decides how fast that work carries the boat.
What the number describes
Treat watts and split as a measure of your effort on the machine. They are excellent for pacing an erg piece, setting interval targets, and comparing one erg effort with another. They are not a prediction of on-water boat speed, and comparing your erg split to a crew’s time on the water will mislead you every time.
Frequently asked questions
Is a 2:00 erg split the same as rowing 2:00 on the water?
No. The Concept2 formula describes the flywheel’s power, not boat speed. On the water your speed depends on the hull, crew weight, rigging, water and wind, so the same split produces very different distances.
Why do watts change so quickly when I drop my split?
Power scales with the cube of pace. Because watts are proportional to one over the split cubed, a small improvement in your 500 m time requires a large increase in power output.
Where does the 2.80 constant come from?
It is the constant Concept2 publishes for the relationship between pace and power on its ergometers, derived from the flywheel work model. It is specific to the erg and is not a measure of on-water performance.
Related tools and reading
Rowing Split calculator
Convert between 500 m split and watts instantly using the Concept2 formula above.
ToolPower-to-weight calculator
Turn your watts into watts per kilogram to compare efforts across body weights.
Sources
- Concept2, pace and watts calculation documentation — the published watts = 2.80 / (pace)³ relationship and its inverse. Checked 24 Aug 2026.