How this instrument works
Rowing splits are conventionally reported as time per 500 metres — a '2:00' split means 500 m would be covered in two minutes at that pace — because 500 m is the standard reference distance across indoor ergometers and on-water racing alike. Watts, by contrast, measure the power actually being produced at the flywheel, and the two aren't linked by a straight line: pace and power follow a cube-law relationship, the same physics that governs a boat pushing through water.
That cube law exists because the ergometer's flywheel loses energy to air drag at a rate proportional to the cube of how fast it's spinning, so a small improvement in split time demands a disproportionately larger increase in power. Going from a slower split to a faster one costs meaningfully more power than the same-sized improvement made further up the pace scale, which is exactly why erg workouts pushing toward a fixed wattage target feel so much harder to hold as the pace drops.
Concept2, the manufacturer behind the PM performance monitors fitted to most gyms' rowing ergometers, publishes this exact pace-to-watts relationship on its own website as the official conversion between the two units its machines display. This instrument reproduces that published formula directly, so a split entered here returns the same wattage figure a Concept2 monitor would show for the same pace.
- Convert a split from minutes:seconds to seconds — e.g. a 1:52 split is 112 seconds.
- Enter Split — seconds per 500 m (sec) — the pace being rowed or targeted.
- Read Pace (sec/m) — the same split expressed as seconds per single metre.
- Read Power (watts) — the wattage that split corresponds to on a Concept2 ergometer.
- Try a few seconds faster or slower to see how sharply watts respond to small pace changes.
Worked example — a 2:00/500m split
Enter 120 into Split — seconds per 500 m (sec) — a 2:00/500m split, a common steady-state training pace for a club-level rower. Pace reads 0.24 sec/m, and Power reads 202.5463 watts.
That comes from pace = 120 ÷ 500 = 0.24, then watts = 2.80 ÷ 0.24³ = 2.80 ÷ 0.013824 = 202.5463. Row 15 seconds faster per 500 m, to a 1:45 split (105 sec), and pace drops to 0.21 sec/m while power climbs to 302.3432 watts — nearly 100 extra watts for a pace change that looks modest on the monitor.
Questions
How do I convert my monitor's split into seconds for this calculator?
Multiply the minutes by 60 and add the remaining seconds — a 1:48 split is (1 × 60) + 48 = 108 seconds, and a 2:03 split is (2 × 60) + 3 = 123 seconds. Most Concept2 PM monitors already display the split in minutes:seconds form, so this conversion is the only extra step needed before entering a figure here.
Why does watts increase so fast as my split time drops?
Because watts scale with the cube of pace, not a straight multiple of it — halving the pace value (rowing twice as fast per metre) multiplies watts by eight, not two. That cube-law relationship is why a rower chasing a personal-best 2k time sees power climb dramatically in the closing strokes even though the split, in seconds, is only dropping by small amounts.
Is erg watts the same as watts on a stationary bike?
Both measure real mechanical power output, so a watt means the same physical thing on either machine, but the two aren't directly comparable as fitness benchmarks — rowing engages a much larger share of total muscle mass per stroke than cycling does per pedal revolution, and the movement patterns differ enough that equal wattage doesn't imply equal difficulty or equal training effect.
How does this relate to my 2,000 m or 500 m personal best?
Average power over a 2k or 500m piece is exactly this formula applied to the average split held for that distance, so a faster time by definition means higher average wattage. Many rowers use that wattage figure specifically to hold an even, controlled effort across a piece, since pacing to a fixed power target makes it obvious in real time if the first half was started too aggressively.
What if my Concept2 monitor doesn't show watts directly?
Older or simpler Concept2 display settings sometimes default to showing only split and calories, hiding watts from the main screen even though the monitor calculates it internally. Checking the display menu usually reveals a watts option to add to the readout, but entering the split shown into this instrument gives the identical figure either way.