Calculate your BMI

To work out your BMI (which can tell you whether you are the ideal weight, under-weight or over-weight) use the tool below:

Your BMI is

BMI Explained

BMI stands for body mass index and is a measure of whether you are a healthy weight for your height.

BMI kg/m2 WHO definition
Below 18.5 Underweight
18.5-24.9 Normal weight
25.0-29.9 Pre-obesity (overweight)
30-40 Obese
>40 Morbidly Obese


If you are underweight you should try and gain some weight or not lose any further weight before your surgery.

If you are overweight, losing some weight before surgery will reduce your chances of a complication.

Managing weight is hard. Changing your diet prior to a stressful event such as surgery is difficult, but can make a real difference. Good quality, evidence based advice gives you the best chance of success.

Useful internet resources

If your weight is something you would like to target, we recommend you take a look at the following resources:

The NHS Weight Loss Plan

NHS - Digital Weight Management

You can find some specific advice for different aspects of nutrition below: