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.

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 90 percent instantly. It takes roughly 60 to 90 seconds to climb into the zone, so the first minute of each interval can read below target even when your effort is exactly right.

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