Fitness Calculators
Free tools to dial in your nutrition, find your training zones, and track key body composition metrics.
Calorie Calculator
Estimate your daily calorie needs for your goals.
Macro Calculator
Get your ideal protein, carb, and fat breakdown.
Heart Rate Zone
Calculate your 5 training heart rate zones.
Body Fat Calculator
Estimate your body fat percentage using the US Navy method.
BMI Calculator
Check your Body Mass Index based on height and weight.
Water Intake
Find your daily water intake recommendation in glasses and liters.
Pregnancy Due Date
Calculate your due date and track pregnancy milestones.
Running Pace
Convert pace to finish time or finish time to pace for any distance.
Fitness numbers are starting points
Fitness math can be helpful, but it is still an estimate. A calorie target gives you a place to start. Heart rate zones make training less random. Body composition numbers can show a trend over time. None of these replace how you feel, how you recover, or what your doctor tells you.
I like these calculators most for reality checks. If your planned cut puts you at an absurdly low calorie intake, the numbers will say so. If your easy run is actually pushing into a hard training zone, that shows up too. The point is not to obsess over every decimal. It is to make better adjustments.
Use the estimates for a few weeks, then compare them with what actually happens. Weight changes, energy levels, sleep, training performance, and appetite all matter. If you have a medical condition, are pregnant, or are changing your diet aggressively, get professional guidance first.
Common questions
- What is macronutrient balance and why does it matter?
- Macronutrients are protein, carbohydrates, and fat. Protein usually gets set first, especially if you are trying to build or keep muscle. Carbs and fats fill in the rest based on training, preference, and how you feel day to day.
- What are training heart rate zones?
- Heart rate zones break effort into rough bands, from very easy to maximum effort. Zone 2 is commonly used for aerobic base work, while higher zones are harder and more taxing. The calculator gives you ranges based on age or max heart rate, then you can adjust based on real workouts.
- How accurate are calorie calculators?
- Calorie calculators estimate your daily expenditure using formulas like Harris-Benedict or Mifflin-St Jeor, which are accurate within about 10-20% for populations on average. However, individual metabolism varies a lot based on genetics, hormone levels, medications, and other factors. Use these estimates as starting points, then adjust based on actual body weight changes over 2-3 weeks.
- Should I focus on weight loss or body composition?
- Scale weight is useful, but it does not tell the whole story. You can lose fat, gain muscle, and see the scale barely move. Measurements, photos, strength numbers, and body fat estimates can add context.