Heart Rate & Pace Calculator
Your max heart rate (HUNT formula), 4x4 zones, and target pace, treadmill speed, rowing split or watts.
Free Fitness Tools
Calculators, a timer and a plan generator for the Norwegian 4x4 and everyday training. Free, no sign-up, nothing leaves your browser.
Every tool is built on published research and explains the formula it uses. Start with your heart rate zones, put a 12-week plan in your calendar, and time each session with the interval timer.
Heart rate
Max heart rate, training zones and how fast your heart recovers.
Zone 2 Heart Rate Calculator
Your Zone 2 range three ways (% max, heart-rate reserve, MAF 180) plus all five zones and the 4x4 targets.
Heart Rate Recovery Calculator
How many beats your heart drops in the first minutes after a hard interval, and what it says about your fitness.
VO₂ max & fitness age
Estimate your aerobic fitness and see how it compares for your age.
VO2 Max Calculator
Estimate VO2 max from resting heart rate, the Cooper test, a 1.5-mile run or a 1-mile walk, and see where you rank.
Fitness Age Calculator
Your fitness age from age, waist, resting heart rate and activity, using the NTNU HUNT fitness model.
Pace, timing & plans
Turn targets into treadmill speeds, rowing splits, a timer and a 12-week calendar.
Norwegian 4x4 Interval Timer
A free full-screen 4x4 timer with beeps and voice cues. Tabata, EMOM and custom intervals too.
12-Week Plan Generator
Pick your start date, level and days. Get a dated 12-week 4x4 plan for your calendar.
Treadmill Pace & Incline Calculator
Convert mph, km/h and min/mile or min/km, and see what an incline is worth in flat-ground pace.
Rowing Pace Calculator
Convert split /500 m, watts, time and distance on a rowing machine, plus 4x4 splits from your 2K.
Body & energy
Calories burned and the waist measure that tracks visceral fat.
HIIT Calorie Calculator
Calories burned in a Norwegian 4x4 or other HIIT session, from your heart rate or the activity.
Waist-to-Height Ratio Calculator
Is your waist under half your height? The simple visceral-fat check, with your target waist.
Which tool do I need?
| I want to… | Use |
|---|---|
| Know my heart rate targets for 4x4 intervals | Heart rate & pace calculator |
| Train easy days at the right intensity | Zone 2 calculator |
| Find out how fit I am, without a test | Fitness age calculator |
| Measure my VO2 max with a run or walk | VO2 max calculator |
| Follow a structured plan | 12-week plan generator |
| Time a session without an app | Interval timer |
| Set treadmill speed and incline | Treadmill pace calculator |
| Set rowing splits and watts | Rowing pace calculator |
| Check my recovery after hard efforts | Heart rate recovery calculator |
| Track belly fat, not just weight | Waist-to-height ratio calculator |
| Know what a session burns | HIIT calorie calculator |
Frequently Asked Questions
Are these tools free?
Yes. Every tool on this page is free, with no sign-up. Everything is calculated in your browser, and nothing you enter is sent to us.
Which tool should I start with?
New to the Norwegian 4x4? Start with the heart rate & pace calculator to get your interval and recovery targets, then the 12-week plan generator to schedule your sessions. Want a baseline? The fitness age calculator needs no exercise; the VO2 max calculator uses a field test.
How accurate are the calculators?
They use published, peer-reviewed formulas: the HUNT formula for max heart rate, the HUNT non-exercise fitness model, the Cooper and Rockport tests, ACSM metabolic equations, Keytel calorie equations and NICE waist-to-height bands. Each page lists its sources. They are estimates for training, not medical tests.
Can I link to or share a result?
Yes. After you calculate, the page address contains your inputs, so the Share button sends a link that opens with the same result. You are welcome to link to any tool from your own site.