Rowers and coaches live in a world of numbers on the Concept2 erg. Splits, watts, paces, distances, heart rate — the machine spits them out every stroke. But raw data can be overwhelming. The real challenge is knowing what those numbers mean and how to use them to train smarter.

That’s where an erg calculator comes in. By converting splits into watts or predicting your on-water 2K times from your erg pace, it turns raw data into actionable insight. The problem? Most athletes — and even some coaches — aren’t sure how to apply those results in practice.

In this article, we’ll answer the five most common questions about erg calculators — from split-to-watts conversions to on the water 2K predictions — and show how smart coaches turn those answers into faster, healthier teams.

Start with our Erg Calculator Hub if you want to try the tools yourself.

Question 1 – How do you convert rowing splits to watts?

On the Concept2 erg, your split time (usually shown as time per 500m) is directly linked to your power output in watts. Watts measure how much power you are producing — the power you put into the flywheel every stroke. Splits, on the other hand, are just how long it takes you to cover 500m at that effort.

The Concept2 formula to convert to Watts is simple:

Watts=2.80(Split in seconds/500)3Watts = \frac{2.80}{(\text{Split in seconds}/500)^3}

Watts=(Split in seconds/500)32.80

That looks intimidating, but in practice it’s straightforward:

• A 1:45 split equals about 302 watts.
• A 2:00 split equals about 203 watts.
• A 2:30 split equals about 137 watts.

💡 Why it matters: Splits don’t scale in a straight line — every second you shave off requires disproportionately more power. For example, moving from a 2:15 split to 2:05 bumps your output from about 142 watts to 179 watts — a 26% increase. But dropping from 1:45 to 1:35 demands a leap from ~302 watts to ~408 watts — a 35% increase, even though both are just a 10-second gain.

Watts cut through this distortion because they rise in a linear way. A jump from 200w to 220w is the same 10% improvement as 100w to 110w. That’s why coaches rely on watts to set training zones and compare athletes fairly (even across sports like cycling, rowing, skiing), while splits remain most useful for pacing specific pieces.

👉 Want to try it? Try our Erg Calculator Hub for instant split-to-watts conversions.

Question 2 – How can you predict a on the water 2K time using an erg calculator?

There is a well-validated relationship between erg outputs on the Concept2 and on-water rowing speed. In calm conditions and with technically skilled rowers, erg predictions are fairly close — you might add 5-10 seconds to your predicted 2K time to allow for real-world inefficiencies. Research by rowing biomechanist Dr. Valery Kleshnev (BioRow) goes even deeper and can be used to also model weather and blade gearing.

💡 Why it matters: An Boat speed calculator gives a controlled benchmark, and helps rower understand how fitness improvements translate to boat speed. It also helps coaches set realistic goals. With the CrewLAB Boat Speed Predictor, you can estimate the impact of improving your crew’s average 2K, adjusting lineups, or swapping in a lighter rower. This turns raw erg data into better expectations before race day.

👉 Want to see how fast your team is? Try our Erg Calculator Hub for instant boat speed predictions.

Question 3 – How do coaches use erg calculators to set training zones?

One of the most powerful uses of an erg calculator is setting training zones. Instead of guessing paces, coaches can translate an athlete’s 2K score or heart rate data into structured training ranges. This helps athletes hit the right physiological targets — from long aerobic base work to high-intensity race prep.

With the CrewLAB Training Zones calculator, athletes can see approximate ranges for RPE, heart rate, watts, and lactate all in one place:

💡 Why it matters: Training zones ensure athletes build the right physiological systems for them without overtraining. Instead of guessing paces, coaches can use erg calculators to set precise targets, keeping entire teams consistent across sessions.

👉 CrewLAB makes this even easier — track each session, apply RPE alongside zone-based work, and see whether athletes are hitting targets over time.

Question 4 – How accurate are erg calculators for training and racing?

Erg calculators are very accurate for measuring power output on the machine. The Concept2 formula reliably converts splits into watts, which makes comparisons between workouts and athletes consistent. That’s why coaches use them as a standard benchmark.

But accuracy has limits:

• Training vs racing: An erg calculator can predict a 2K time, but it doesn’t account for fatigue, life stress, sleep issues, mental toughness, or race-day pressure.
• On-water conditions: Current, wind, and boat class introduce variables that calculators can’t fully capture.
• Technique differences: Two athletes with identical erg watts may move a boat differently depending on efficiency and skill.

💡 Why it matters: Erg calculators are excellent for establishing training targets and tracking fitness, but they should be paired with wellness checks and technical feedback. That’s why CrewLAB combines erg data with RPE, attendance, and wellness tracking — giving coaches the full picture, not just the numbers.

👉 Explore the Erg Calculator Hub.

Question 5 – Can erg calculators help compare athletes of different sizes?

One of the most common challenges in rowing is comparing a lightweight athlete to a heavyweight. Splits and Power alone don’t tell the full story, since bigger athletes have to move more mass. An erg calculator helps solve this by using the Bot speed Predictor — Add the erg power and weight of each athlete one at a time and see who is predicted to moved boats faster.

For example:

• A 90kg athlete doing a 2k erg at 1:45 split (~302w) would get a 2k on water time of 7:57 in a 1x.
• A 70kg athlete doing a 2k erg at 1:48 split (~263w) would get a 2k on water time of 7:53 in a 1x.

💡 Why it matters: Looking at power-to-weight ratios gives coaches a fairer picture of athletic potential, especially when selecting crews or evaluating development. It helps identify athletes who might not pull the fastest raw erg split but deliver better boat speed.

👉 CrewLAB makes this simple — giving coaches the data they need to make better lineup decisions.

More Resources

• Athlete Wellness Guide – A coach’s toolkit for tracking wellness signals like sleep, stress, and recovery.
• The Coach’s Guide to RPE – How to use Rate of Perceived Exertion as the gold standard for endurance monitoring.
• Athlete Management Software – The Science of Athlete Profiles: A Smarter Way to Track Training and Performance
• YouTube: CrewLAB Coaching Insights – Practical videos on monitoring, athlete engagement, and team culture.