How does StrongLifts calculate the calories of my workout?

Our formula for estimating calories burned is based on this study.

In short, lifting weights burns about 5-6kcal/min or ~300kcal/hour (the equivalent of brisk walking).

Doesn't lifting weights burn more than 300kcal/hour?

Lifting weights doesn't burn as many calories per minute as activities like running or cycling. This is because you spend most of your time resting between sets. If you want to burn a lot of calories quickly, doing cardio exercises like running or swimming is more effective.

However, the primary goal of lifting weights is not to burn calories but to get stronger and build muscle. Having more muscle increases how many calories you burn when not exercising. This extra muscle mass requires more energy to maintain. Repairing your muscles after a workout also burns calories. Studies found that regular resistance training can increase your daily energy expenditure by 100 calories or more (source). So, even though you might not burn that many calories while lifting weights, it helps you burn more calories overall.

Lifting weights also strengthens your muscles, bones, and joints in ways that cardio doesn't. Just looking at how many calories you burn during a workout doesn't show all the benefits of lifting weights. The main metrics we recommend looking at are 1) consistency (getting 2-3 workouts done each week) 2) increasing your strength (which you can track in the progress graphs inside StrongLifts). Consistently doing your workouts and trying to add weight over time will increase your strength, muscle mass, and bone density. This will improve your overall health.

Also, if your goal is to lose a lot of weight, lifting weights or cardio alone isn't effective unless you can do hours of it. See: https://pubmed.ncbi.nlm.nih.gov/24438736/

This study found that if you want to lose a lot of weight, you need a calorie restriction. You have to eat less. Lifting and cardio are great. But unless you can do hours of it to burn a lot of calories, it won't be enough. Most of us can't do hours of exercise because we're busy with work, family, etc. And so we need to improve our diet if we want to lose a lot of weight.