Data Source and Methodology

This calculator uses established formulas to provide accurate, reliable estimations. We believe in transparency and cite our sources clearly.

  • Calories Burned: Calculations are based on the Metabolic Equivalent of Task (MET) values. The MET values for the activities listed are sourced from the "2011 Compendium of Physical Activities," a comprehensive guide developed by Dr. B. E. Ainsworth and colleagues.
    Source: Ainsworth, B. E., et al. (2011). 2011 Compendium of Physical Activities: a second update of the codes and MET values. Medicine & Science in Sports & Exercise.
  • Heart Rate Zones: Calculations are based on guidelines from the American Heart Association (AHA). The default calculation uses the standard Fox formula (220 - Age). When a Resting Heart Rate is provided, the calculator uses the more individualized Karvonen formula.

The Formulas Explained

Here are the exact equations used by the calculator, presented for full transparency.

Calories Burned (METs)

The formula to estimate calories burned per minute is:

$$ \text{Calories/min} = \frac{(\text{MET} \times \text{Body Weight (kg)} \times 3.5)}{200} $$

Total calories are then found by multiplying this value by the duration of the activity in minutes.

Maximum Heart Rate (MHR)

The most common formula (Fox formula) used to estimate MHR is:

$$ \text{MHR} = 220 - \text{Age} $$

Target Heart Rate (Karvonen Formula)

When you provide a Resting Heart Rate (RHR), the calculator uses the Karvonen formula to find your target zones, which is more accurate as it accounts for your individual fitness level.

$$ \text{Target HR} = ((\text{MHR} - \text{RHR}) \times \%intensity) + \text{RHR} $$

Glossary of Variables

MET (Metabolic Equivalent)
A measure of exercise intensity. One MET is the energy expended while sitting at rest.
Body Weight (kg)
Your mass in kilograms. The formula requires this unit, so the calculator converts from pounds if necessary (1 lb = 0.453592 kg).
Age
Used to estimate your maximum heart rate.
RHR (Resting Heart Rate)
Your heart rate in beats per minute (bpm) when you are at complete rest, typically measured just after waking up.

How It Works: A Step-by-Step Example

Example: Calculating Calories Burned

  1. Inputs:
    • Activity: Jogging, general (MET value of 7.0)
    • Weight: 150 lbs
    • Duration: 30 minutes
  2. Step 1: Convert Weight
    $ 150 \text{ lbs} \times 0.453592 = 68.04 \text{ kg} $
  3. Step 2: Calculate Calories per Minute
    $ (7.0 \text{ MET} \times 68.04 \text{ kg} \times 3.5) / 200 = 8.33 \text{ Calories/min} $
  4. Step 3: Calculate Total Calories
    $ 8.33 \text{ Calories/min} \times 30 \text{ minutes} = \textbf{250 Calories} $

Frequently Asked Questions (FAQ)

What is a MET value?

A MET, or Metabolic Equivalent, is a ratio of your working metabolic rate relative to your resting metabolic rate. It's a standardized way to measure the intensity of an activity. A MET of 1 is resting. An activity with a MET of 7 (like jogging) means you are expending 7 times the energy you would at rest.

Why is my calculated calorie burn different from my smartwatch?

Smartwatches and fitness trackers use additional data, primarily your heart rate, to estimate calorie burn. This MET-based calculator provides a standardized, population-based estimate, which is excellent for comparison. Your watch provides a more personalized (but not always more accurate) estimate based on your body's real-time response.

What is the difference between the simple MHR and the Karvonen formula?

The simple formula ($ 220 - \text{Age} $) is a general guideline that works for most people. The Karvonen formula is more advanced because it uses your heart rate reserve ($ \text{MHR} - \text{RHR} $). This is the "usable" range of your heart rate. It provides training zones that are more personalized to your specific cardiovascular fitness level.

What heart rate zone is best for fat loss?

The "fat-burning zone" is typically Zone 2 (60-70% of MHR). In this zone, your body uses a higher *percentage* of fat for fuel. However, higher-intensity workouts (Zones 3-4) burn more *total* calories in the same amount of time, which is the most important factor for weight loss. A balanced routine includes both.

How often should I measure my resting heart rate?

For the most accurate reading, measure your RHR first thing in the morning, before you get out of bed or drink caffeine. Do this for 3-5 consecutive days and take the average. As your cardiovascular fitness improves, your RHR will typically decrease, so it's good to re-check it every few months.

Tool developed by Ugo Candido.
Health and fitness content verified by the CalcDomain Editorial Board, including certified exercise physiologists and nutritionists.
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