What formula does this predictor use?

It uses the rowing power-pace relationship, often called Paul's Law, which states that pace per 500 metres changes by about one second for each doubling or halving of distance. Mathematically the time scales with distance raised to an exponent near 1.06, capturing how pace slows over longer pieces.

How accurate is a 2K prediction from another distance?

Predictions are most accurate when the test piece is close to 2K and is a genuine maximal effort. A 5K or 6K predicts a 2K reasonably well; very short sprints or very long steady-state pieces are less reliable because they rely on different energy systems.

What is the confidence range for?

The range shows a realistic spread around the point estimate because the scaling exponent varies between athletes and pacing affects results. Treat the middle figure as your target and the range as the band most well-paced races fall into.

Does this work for both rowing and the erg?

The scaling rule was derived from Concept2 erg data and is most reliable there. On-water rowing adds wind, stream, boat, and rigging variables, so use the erg estimate as a guide and expect more variation on the water.

Why does pace slow down over longer distances?

Over longer pieces you must hold a lower power output to avoid blowing up, because aerobic capacity and fatigue limit sustainable output. The power-law exponent above one encodes this: doubling distance costs you a few seconds per 500 metres of pace.

What is the Rowing 2K Time Predictor?

Input the time and distance of any rowing erg piece to estimate your 2000 m time using the Paul's Law power-pace scaling rule, with a confidence range that accounts for race-day variation and pacing. It runs free in your browser on Gera Tools, with nothing uploaded.

Rowing 2K Time Predictor

Name: Rowing 2K Time Predictor
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This tool predicts your 2000 m rowing erg time from any other maximal test piece using the well-established power-pace relationship in rowing, sometimes called Paul’s Law. Enter a 5K, 6K, 1K or any timed distance, and it scales the result to an equivalent 2K with a confidence range.

How it works

Rowing pace and distance follow a power law. If t1 is your time over distance d1, the predicted time t2 over distance d2 is:

t2 = t1 × (d2 / d1) ^ k

The exponent k is about 1.06 for rowing — slightly above 1, which is why pace per 500 m slows as distance grows. This is equivalent to Paul Smith’s rule of thumb that your 500 m split changes by roughly one second per doubling or halving of distance. The predicted 2K is then converted to a 500 m split:

split per 500 m = predicted 2K time / 4

A confidence range is shown by evaluating the formula at exponents of 1.04 and 1.08 to reflect athlete-to-athlete variation.

Example

A 6000 m piece rowed in 24:00 predicts a 2K of about 24:00 × (2000 / 6000) ^ 1.06 ≈ 7:34, a 500 m split near 1:53. For the most reliable prediction, test with a distance within a factor of three of 2K and row it as a true maximal effort with even pacing. Sprints under 1K and long steady pieces over 10K push the formula outside its reliable range, so use those only as rough guides.

Choosing the right test piece

The accuracy of any 2K prediction depends heavily on which piece you use as input and how you row it:

Best distances for prediction: 5K and 6K pieces are the most popular among competitive ergers precisely because they translate well to a 2K via the power law. They are long enough to test aerobic capacity seriously, short enough to be genuinely maximal, and close enough to 2K (within a factor of three) that the scaling exponent stays in its reliable range.

What makes a valid test piece:

It must be a genuine, near-maximal effort — not a controlled aerobic piece or a training row with a ceiling heart rate.
Pacing should be as even as possible. A wildly positive split (too fast early, blow-up late) will give an overly optimistic 2K. A negative split or very conservative start gives a pessimistic result.
The piece should be rowed on an erg in drag-factor conditions comparable to what you would use for a real 2K, since drag factor affects split times.

Less reliable sources:

Pieces shorter than 1K draw heavily on anaerobic capacity, which does not extrapolate well to the predominantly aerobic 2K.
Pieces longer than 10K or 60-minute steady-state rows test different pacing strategies and energy system contributions, so the predicted 2K from them tends to be pessimistic.

Understanding the confidence range

The confidence range shown around the central prediction comes from evaluating the formula at exponent values slightly above and below 1.06 (roughly 1.04 to 1.08). This reflects the fact that the power-law exponent varies between individuals — some rowers are relatively better at shorter, more anaerobic efforts and some are stronger over longer, more aerobic pieces. If your training skews heavily toward one end, your personal exponent may sit outside the range shown. Use the middle figure as your target and treat the range as the realistic spread for a well-paced effort.