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, 2026Last updated September 12, 2026By Archline Labs LLCEditorial 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.

Age

Years

Max HR formula

Used only if no measured max below

Measured max HR (optional)

Overrides the formula

Resting HR (optional)

Enables Karvonen targets

Hard interval · 85 to 95%

156 to 175 bpm

Hold this for each 4-minute interval

Recovery · 60 to 70%

110 to 129 bpm

Easy effort between intervals

Based on an estimated max heart rate of 184 bpm (Tanaka).

These numbers are estimates. Formula-based max heart rate can be off by 10 to 20 bpm for any individual, so use them as a starting point and let perceived effort guide you. The Norwegian 4x4 is intense, so if you have a heart condition, high blood pressure, or any medical concern, talk to your doctor before starting. This page is educational and not medical advice.

How the calculator gets your numbers

Calculator formulas

Estimated max HR: 208 − (0.7 × age), using Tanaka by default
Hard interval: estimated or measured max HR × 0.85 to 0.95
Active recovery: estimated or measured max HR × 0.60 to 0.70
Optional HR reserve: resting HR + intensity × (max HR − resting HR)

A measured maximum heart rate overrides the age estimate. Formula results are population-level estimates, so use the calculated band as a starting point and keep the effort repeatable across all four intervals.

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.

Norwegian 4x4 heart-rate zones by estimated max HR
Estimated max HR	Hard interval (85 to 95%)	Recovery (60 to 70%)
170 bpm	145 to 162 bpm	102 to 119 bpm
180 bpm	153 to 171 bpm	108 to 126 bpm
190 bpm	162 to 181 bpm	114 to 133 bpm
200 bpm	170 to 190 bpm	120 to 140 bpm

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. The same percentage of HR reserve is not equivalent to the same percentage of max HR. Keep the standard 85–95% max-HR band as the protocol target; HRR is shown only for comparison.

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.

Turn your heart-rate zone into pace and incline

The calculator gives you the physiological target, not one universal treadmill speed. Start at a controlled pace, then use your response late in the interval to adjust the next one.

Pace so interval four looks like interval one. If the last rep falls apart, you went out too hard.
On a treadmill, begin with 1 to 2% incline. If speed feels unsafe, hold it steady and add incline gradually instead.
If you remain below your zone late in the interval, add 0.2 to 0.5 mph (0.3 to 0.8 km/h) or 1 to 2 incline points before the next rep.
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.

See the Norwegian 4x4 treadmill speed and incline guide for example starting ranges by fitness level and mph-to-km/h conversions.

Keep going

Norwegian 4x4 timer → Run the warmup, four intervals, recoveries, and cooldown on a guided 4x4 interval timer. The full Norwegian 4x4 guide → Protocol, evidence, mistakes, and everything else about the workout.

Calculator FAQ

What heart rate should I hit during Norwegian 4x4 intervals?

Aim for 85 to 95 percent of your maximum heart rate during each 4-minute interval, ideally drifting up toward 90 percent or higher by the end. Recover at about 60 to 70 percent between intervals.

How do I estimate my max heart rate for the calculator?

The Tanaka formula (208 minus 0.7 times your age) is more accurate across ages than the older 220-minus-age rule. Best of all is a max you have actually measured in a hard effort. The calculator accepts age, a measured max, and an optional resting heart rate.

Why is my heart rate below target at the start of an interval?

Heart rate lags behind effort, so the beginning of a hard interval can read low even when the effort is appropriate. In our N=1 field analysis, the median sustainable ramp was 2 minutes 11 seconds, with wide variation between intervals and sessions.

Reference

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

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