Erg Watts to Split Converter

The Concept2 cubic relationship

Every Concept2 erg uses one equation to convert between power and pace:

watts = 2.80 ÷ (split ÷ 500) ^ 3

where split is in seconds per 500m. The flip:

split_seconds = 500 × (2.80 ÷ watts) ^ (1/3)

Why a cube? Because water resistance, and Concept2’s air resistance which mimics it, scales with the cube of velocity. To row twice as fast you need eight times the power. The PM5 monitor does this math hundreds of times per second; the calculator above does it once.

Reference table: the splits and watts every rower memorises

Look at what the cube does at the bottom of that table. Going from 1:30 to 1:15 is fifteen seconds, and it costs you 350 extra watts, more than the entire output of the 2:00 steady-state row. That is why the last ten seconds of a 500m sprint feel the way they do, and why shaving two seconds off a 2K split is a genuinely different project from shaving two seconds off a 5K.

The watts column is “average watts the flywheel sees.” Power on the handle is higher; the difference is drivetrain efficiency, fan damping setting, and the impossibly short recovery between strokes.

Damper setting does not change the formula

A common beginner question: does damper setting change watts? No. The same wattage produces the same split regardless of damper. What changes is how the stroke feels (heavier or lighter) and the optimal stroke rate. Most coaches set damper 3 to 5 for endurance work, 5 to 7 for power work. Setting it to 10 turns the erg into a strength training tool, not a rowing simulation.

Why bigger rowers go faster

The erg ignores body weight. Nothing has to be lifted or floated, so absolute power sets the split, and bigger rowers produce more absolute power because they have more muscle. A 200 lb (91 kg) heavyweight holding 350 watts is producing 3.9 watts per kg. A 130 lb (59 kg) lightweight holding the same 350 watts is producing 5.9, a far rarer engine for its size, yet the monitor shows both the same 1:40. On the water the lightweight’s boat carries 32 kg less, so that rower is more competitive than the erg score suggests.

The PR rule

If you have a strong PR over 2K and want to know what watts to hold for a 5K, multiply your 2K watts by about 0.85. For a 10K, multiply by about 0.75. For a 60-minute test, roughly 0.66.

Those factors are not guesses; they fall straight out of Riegel’s formula, the time-versus-distance power law that rowing borrowed from running. It says a 5K takes (5000 ÷ 2000)^1.06 = 2.64 times as long as a 2K, which makes the 5K pace 5.7% slower, and the cube turns that 5.7% into a 15% cut in watts. The same arithmetic gives 0.75 at 10K.

Paul’s Law, rowing’s own rule of thumb, gets there a different way: add 5 seconds to the split for every doubling of distance. On a 1:52.5 2K split it puts the 5K at 1:59.1, within half a second of Riegel. For a much faster rower the flat five seconds bites harder, and the 5K factor drops nearer 0.81.

A useful sanity check: if your actual 5K watts are well below 0.85 of your 2K, your aerobic base is the limiter. If they are above it, your 2K is leaving something on the table at the top end.