Exercise Intensity Calculator

Exercise Intensity Calculator

Heart Rate Zone Analysis

Exercise Intensity
Calculator

Powered by the Karvonen Heart Rate Reserve method. Enter your profile and zone times to get your target HR, intensity score, and recovery recommendations.

Athlete Profile

HRmax estimated via Tanaka Formula: 208 − (0.7 × Age)

Target HR per Zone

Target HR = (HRmax − HRrest) × I% + HRrest

Zone Intensity Ranges

Time in Each Zone

Total: 0 min

Exercise Intensity Results

Intensity Score
0
out of 480 max
Intensity %
0%
unified model
Intensity Minutes
0
Z2=1×, Z3–Z5=2×
Strain Index
0
relative effort
0 Rest20 Easy40 Moderate60 Hard80+ Peak
⬤  Enter your data

Aerobic / Anaerobic Split

Aerobic Z1–Z3
0%
of total session
Anaerobic Z4–Z5
0%
of total session
Enter zone times to see your recovery recommendation.

Steadfast Recovery Stack

Enter your session data

One focused product per nutritional need — matched to your intensity zone from Steadfast Nutrition's range.

Complete Product Reference
# Product Category Protein (g) Carbs (g) Fats (g) Kcal Serving Ratio
Methodology

Karvonen Formula

Target HR =
(HRmax − HRrest)
× Intensity% + HRrest

Gives the target heart rate for a specific exercise intensity, accounting for your individual resting HR (Heart Rate Reserve method). More personalised than raw HRmax percentages.

Intensity Score

Score =
(Z2×1) + (Z3×2)
+ (Z4×4) + (Z5×8)

Weights mirror metabolic cost doubling at each threshold. Max = 480 pts (60 min in Z5). Intensity % = Score ÷ 480 × 100.

HRmax Estimation

HRmax = 208 − (0.7 × Age)

Tanaka Formula — more accurate than 220−age for adults over 40. Override manually if you have a lab-tested HRmax value.