Calorie Crunch

About Calorie Crunch

Calorie Crunch is a free, open-source calorie and macronutrient calculator that runs entirely in your browser. No sign-ups, no tracking, no data collection — just plug in your numbers and get science-backed estimates for your daily nutrition targets.

The Science

Mifflin-St Jeor Equation

The default formula for estimating Basal Metabolic Rate (BMR). Published in 1990, it's considered one of the most accurate predictive equations for the general population.

Male: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Katch-McArdle Formula

Used when body fat percentage is provided. It factors in lean body mass, making it more accurate for people who know their body composition — especially useful for athletes or those with above-average muscle mass.

LBM = weight × (1 − body fat / 100)
BMR = 370 + 21.6 × LBM
TDEE & Activity Multipliers

Your Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. These multipliers are based on the Harris-Benedict activity scale, widely used in sports science and clinical nutrition.

Sedentary Little to no exercise ×1.2
Light 1–3 days/week ×1.375
Moderate 3–5 days/week ×1.55
Active 6–7 days/week ×1.725
Very Active Athlete / physical job ×1.9

Frequently Asked Questions

How accurate are these calculations?

The formulas used are well-established in nutrition science and provide solid estimates for most people. That said, individual metabolism varies — factors like genetics, hormones, sleep, and stress all play a role. Use the results as a starting point and adjust based on real-world progress.

Should I use the body fat percentage field?

If you know your body fat percentage (from a DEXA scan, calipers, etc.), entering it will switch to the Katch-McArdle formula, which accounts for lean body mass. This tends to be more accurate, especially if you carry more muscle than average.

Where is my data stored?

Nowhere. Your inputs are encoded in the URL so you can bookmark or share your results, but nothing is ever sent to a server. Close the tab and it's gone.

How do I save or share my results?

Just copy the URL from your browser's address bar — your inputs are embedded in it. Bookmark it to revisit later, or send it to someone else and they'll see the same results.

Does Calorie Crunch work on mobile?

Yes. The interface is fully responsive and works on any modern browser — phone, tablet, or desktop. No app install needed.

Is Calorie Crunch free?

Yes, completely free with no ads, no premium tier, and no catch.