What the TDEE to BMI goal weight calculator does
This tool answers two linked questions at once. First, it converts a target BMI into an exact goal weight for your height. Second, it uses your TDEE (Total Daily Energy Expenditure, the calories you burn on an average day) to work out the daily calorie deficit or surplus that moves you from your current weight to that goal weight within a timeframe you choose.
In short: pick the BMI you are aiming for, tell the calculator how many calories you burn, and it returns the weight you are heading toward plus a daily calorie budget to get there.
How to use it
Enter your height in centimetres and your current weight in kilograms. Add your TDEE in calories per day; if you do not know it, calculate it first with a TDEE calculator. Choose a target BMI (18.5 to 24.9 is the normal-weight range) and a timeframe in weeks. The result shows your goal weight, how many kilograms you need to lose or gain, the total energy involved, and the daily calorie deficit or surplus alongside a recommended daily intake.
The formula explained
Goal weight comes straight from the BMI definition, rearranged to solve for weight:
$$ W_{goal} = \text{BMI}_{target} \times \left( \frac{h}{100} \right)^2 $$where h is height in centimetres. The daily calorie change uses the widely cited rule that one kilogram of body mass is worth about 7,700 kcal (equivalently 3,500 kcal per pound):
$$ \text{Daily change} = \frac{ |W_{now} - W_{goal}| \times 7700 }{ \text{weeks} \times 7 } $$Your recommended intake is then your TDEE minus that number to lose weight, or plus it to gain:
$$ \text{Target intake} = \text{TDEE} \pm \text{Daily change} $$Worked example
Suppose you are 175 cm tall, weigh 80 kg, have a TDEE of 2,500 kcal, and want to reach a BMI of 22 over 12 weeks. Goal weight is 22 multiplied by 1.75 squared, which is 22 times 3.0625, or about 67.4 kg. You therefore need to lose 12.63 kg. That is 12.63 times 7,700, roughly 97,200 kcal, spread over 84 days, a deficit of about 1,157 kcal per day. Subtracting that from your 2,500 kcal TDEE gives a target intake of about 1,343 kcal per day.
Frequently asked questions
Do I need my TDEE to use this? You need it for the calorie part. Goal weight only depends on your height and target BMI, but the daily-calorie budget compares your intake against the energy you burn, which is exactly what TDEE measures.
How accurate is the 7,700 kcal per kilogram figure? It is a well-established approximation (often called the 3,500-calorie rule) and is fine for planning. In reality your metabolism adapts as you lose weight, so progress usually slows over time and you may need to reassess.
Is the recommended intake always safe? Not necessarily. Very aggressive timeframes can push intake below healthy limits. As a general guide, do not eat below about 1,200 kcal per day (women) or 1,500 kcal per day (men) without medical supervision; instead, extend the timeframe.
