How this page is reviewed
| Risk tier | YMYL |
|---|---|
| Author | Calculover Editorial Team Health education |
| Editorial owner | Calculover Nutrition & Fitness Desk Wellness methodology owner |
| Reviewer | Calculover Editorial Review Medical-source review |
| Last reviewed | 2026-05-11 |
| Last verified | 2026-05-11 |
| Data effective date | 2026-05-11 |
Methodology
Heart Rate Zones Resource uses the formula or training model documented on the page, such as age-based heart-rate zones, pace conversion, estimated energy cost, power-to-weight ratio, or one-rep-max estimation. Outputs are training estimates intended to help users plan intensity, not clinical exercise clearance.
Assumptions
- Inputs such as age, distance, duration, weight, load, heart rate, and perceived effort are measured consistently and entered in the selected units.
- Age-predicted heart-rate and performance formulas describe averages and can differ meaningfully from measured laboratory or coach-supervised testing.
- The user is healthy enough for the selected activity and will adjust intensity for heat, altitude, injury status, medications, and current conditioning.
Limitations
- Exercise estimates may be unreliable for users with cardiovascular disease, pregnancy, recent illness, injury, heat illness risk, medications that affect heart rate, or symptoms such as chest pain or fainting.
- One-rep-max, power, pace, and calorie formulas do not account for technique, fatigue, terrain, equipment, hydration, sleep, or injury history.
- Use conservative loads and intensities; stop activity and seek medical help for severe shortness of breath, chest pain, fainting, or symptoms that feel unusual.
Sources
- Target Heart Rates Chart, American Heart Association
- How to Measure Physical Activity Intensity, Centers for Disease Control and Prevention
- Physical Activity Fact Sheet, World Health Organization
Professional guidance: Heart Rate Zones Resource supports fitness planning only and is not medical advice, diagnosis, rehabilitation, or exercise clearance. Ask a healthcare professional about safe activity levels if you have symptoms, chronic conditions, pregnancy, medication concerns, or recent injury.
Heart rate zones are training intensity ranges defined as percentages of your maximum heart rate (MHR), typically divided into 5 zones from easy recovery to maximum effort.
The Five Zones
- Zone 1 (50-60% MHR): Recovery — very easy, conversational pace
- Zone 2 (60-70%): Aerobic base — fat burning, endurance building
- Zone 3 (70-80%): Tempo — moderate effort, improves efficiency
- Zone 4 (80-90%): Threshold — hard effort, builds speed and power
- Zone 5 (90-100%): Maximum — all-out sprints, very short duration
Calculating Your Max Heart Rate
The simplest estimate: MHR = 220 − age. For a 35-year-old: 220 − 35 = 185 bpm. More accurate formulas exist (Tanaka: 208 − 0.7 × age), and a lab test provides the most precise measurement.
Real-World Example
A 40-year-old runner with MHR of 180 bpm. Zone 2 (endurance): 108-126 bpm. Zone 4 (threshold): 144-162 bpm. Most training (80%) should be in Zones 1-2, with 20% in higher zones for speed development.
Frequently Asked Questions
Which heart rate zone burns the most fat?
Zone 2 (60-70% MHR) uses the highest percentage of fat for fuel. However, higher zones burn more total calories per minute. For overall fat loss, total calorie expenditure matters more than the "fat burning zone."
How long should I train in each zone?
The 80/20 rule is widely used: 80% of training time in Zones 1-2 (easy) and 20% in Zones 3-5 (hard). This polarized approach builds endurance while allowing adequate recovery.
Is the 220-minus-age formula accurate?
It provides a rough estimate with a standard deviation of ±10-12 bpm. Some people have naturally higher or lower max heart rates. For precise training, consider a lab-based VO2 max test or a field test.