Start with your maintenance calories
First estimate your TDEE — the calories you burn in a day. Eating at that level maintains weight. To lose weight, eat below it. Our calorie calculator estimates your TDEE from your height, weight, age, sex and activity using the Mifflin–St Jeor equation.
How big a deficit?
A 250–500 kcal daily deficit is a sustainable starting range for most people (roughly 0.25–0.5 kg per week). Bigger deficits speed things up but are harder to stick to and can cost muscle and energy. We floor targets at 1,200 kcal.
Make the calories count
Prioritise protein (helps preserve muscle and keeps you full), plenty of vegetables and fibre, and drinks without added sugar. Track for a couple of weeks, then adjust based on real-world results rather than the theory.