Why slow and steady wins
Losing weight quickly sounds great, but most of what comes off fast is water and muscle, not fat. Very fast loss can cause tiredness, hair loss and gallstones, and it slows your metabolism, so the weight tends to come back. A steady pace of about 0.5–1 kg a week protects your muscle and builds habits that last.
How this calculator decides your pace
For most adults with a healthy weight, we use up to 0.75 kg a week. If your BMI is 25 or more, the limit is about 1 kg a week or 1% of your body weight, whichever is higher. With a BMI of 30 or more, it can go up to 1.25% of your body weight, never more than 1.5 kg a week. For teens we use a gentler pace. These limits follow NHS, CDC and NICE guidance.
Your healthy weight range
The calculator also shows the weight range that equals a BMI of 18.5 to 24.9 for your height. A goal below that range isn't recommended. BMI isn't perfect (it doesn't know about muscle), but it's a useful guide for most people.
Make the plan real
Our Weight Loss Tracker turns this into a daily habit: it checks that your goal is healthy, suggests one if you're unsure, and lets you log your weight on a cute digital scale. It's a web app, so there's no download, no account and no subscription.