The honest answer is a range, not a number — and the figure most people choose is far too low to survive contact with a normal month.
That's it. Everything else is detail.
Your resting burn is mostly driven by your size. Multiply it for how active you are and you get maintenance — the amount where your weight holds steady. For most adults that lands somewhere between 1,800 and 2,800.
The calculator works it out using the Mifflin-St Jeor equation, which is the one dietitians generally reach for.
Fifteen to twenty per cent is the range worth staying in. On a maintenance of 2,500 that's a target of 2,000 to 2,125, and roughly half a kilo a week.
Bigger deficits lose weight faster for about three weeks and then stop working, because you're hungry, tired and making worse decisions. The limiting factor was never how fast you could lose — it's how long you can keep going.
Commonly around 1,500 for men and 1,200 for women, though take advice if you're unsure. If the maths wants to go lower, eat the floor and be patient, or move more rather than eating less.
Going under it is the most reliable route to bingeing there is, and a binge costs more than the week of restriction ever saved.
Because it feels proportionate to how badly they want it. But a target you resent is one you'll abandon by week three — and then you're eating at maintenance anyway, while feeling like a failure.
A number you can live with for six months beats a better number you'll keep for ten days. Most people get that trade the wrong way round.
Any calculator is an estimate; real needs vary by around ten per cent either way. Eat to your number for a fortnight, weigh daily, and read the trend rather than any single morning. If nothing's moved, take another 100 or 200 off. Don't start again from scratch.
Leeway is a free tool that does this arithmetic for you. Put what's coming up into the week and it spreads the cost across the days around it, with a floor it won't plan below.
Open the planner — freeLeeway is a planning tool, not medical or dietary advice. Calorie figures are typical estimates and vary by brand, measure and recipe. It isn't suitable if you have, or have had, an eating disorder or a disordered relationship with food. If you're unsure what a safe calorie target is for you, speak to a GP or registered dietitian first.