Norwegian 4x4 Heart Rate Calculator

The Norwegian 4x4 is paced by heart rate, so the first thing you need is two numbers: your hard-interval target (85 to 95% of max HR) and your recovery zone (60 to 70%). Enter your details below to get both, then take them into the workout.

Published June 15, 2026·Last updated July 24, 2026·By Archline Labs LLC·Editorial methodology

Calculate your 4x4 heart-rate zones

Enter your age to get your personal zones. If you know your true max heart rate, enter it for a more accurate result. Add your resting heart rate for optional Karvonen (heart-rate-reserve) targets.

The two Norwegian 4x4 heart-rate zones

The whole workout runs between two targets:

Hard interval zone: 85 to 95% of max HR

Each 4-minute interval lives in the 85 to 95 percent band, ideally pushing toward the top by the final minute. This is the window that makes the 4x4 a well-studied way to train VO2 max: long enough at a high percentage of effort to provide a real stimulus, but controlled enough to repeat four times. If you never get near it, you are doing a tempo session rather than VO2 max work.

Recovery zone: 60 to 70% of max HR

The three minutes between intervals are active recovery at 60 to 70 percent. Keep moving so your heart rate settles back down without crashing to a standstill, which would make the next interval feel like a cold start.

Estimating your max heart rate

The zones are a percentage of your maximum heart rate, so the calculator needs that number first. In order of accuracy:

• A measured max beats any formula. If you have seen a true max in a hard hill effort or a max-HR test, enter it in the calculator.
• Tanaka: max HR is about 208 minus (0.7 times your age). More accurate across ages than the classic rule, which is why it is the calculator default.
• Classic: max HR is about 220 minus your age. Simple, but it drifts for older and younger athletes.

Optional: Karvonen (heart-rate reserve)

If you add your resting heart rate, the calculator also shows a Karvonen estimate. Heart-rate reserve uses the gap between your resting and max heart rate, so it personalizes the target to your own range. It tends to read a little higher than a plain percentage of max HR. Either approach is fine for the 4x4; pick one and stay consistent so your sessions are comparable.

Heart rate lags, so pace by effort too

One number the calculator cannot give you is patience. When a hard interval starts, your heart rate does not jump to the target instantly. In our N=1 analysis of seven Norwegian 4x4 workouts, the median sustainable ramp was 2 minutes 11 seconds, with wide variation between intervals and sessions.

Treat the zone as a guide, not a pass-or-fail line at every second. Start each interval at a hard but repeatable effort, then let your heart rate catch up and settle near the target through minutes 2 to 4. Judge the interval by where you spend the bulk of it, not by the first 30 seconds.

Practical pacing tips

• Pace so interval four looks like interval one. If the last rep falls apart, you went out too hard.
• On a treadmill, use incline to reach the zone without risky speeds. On a bike, hold resistance and a steady cadence.
• Wrist heart rate can lag during fast changes. A chest strap reads sudden jumps more accurately if you want precise interval data.
• Recheck your zones if your fitness changes or you confirm a new measured max.

Keep going

Calculator FAQ

Reference

• Tanaka H, Monahan KD, Seals DR. "Age-predicted maximal heart rate revisited." Journal of the American College of Cardiology, 2001. PubMed