About this calculator
Enter your details, a target weight within the healthy range and your planned daily intake. Targets below the healthy range and intakes below safe limits are not planned.
How to use it
- Enter your details and current weight.
- Enter a target weight and planned daily intake.
- Choose your activity level.
The formula
- daily deficit
- maintenance calories − planned intake
- 7,700
- approximate kcal in 1 kg of body weight
Worked example
A 30-year-old man, 170 cm, 80 kg, aiming for 72 kg on 2,000 kcal
- Maintenance at 80 kg: about 2,662 kcal.
- Deficit = 662 kcal a day, about 0.6 kg a week.
- Reaching 72 kg takes about 14 weeks.
What the result means
As weight falls, maintenance falls too, so later weeks slow down; plan for it to take a little longer than shown.
Assumptions
- Activity stays the same.
Limitations
- Not for anyone with an eating disorder, diabetes or other conditions without medical advice.
Frequently asked questions
How big a deficit is safe?
About 300 to 700 kcal a day for most adults, giving 0.25 to 0.75 kg a week.
Why won’t the calculator accept my target?
It is below the healthy weight range for your height. Please speak to a doctor before aiming lower.
Can I eat less to lose faster?
Very low intakes make you lose muscle and are hard to keep; the calculator does not plan below about 1,200 (women) or 1,500 (men) kcal.
Not medical advice. This calculator is a general screening tool and cannot diagnose any condition. Results are estimates. Please talk to a doctor or a qualified health professional about your health and before making changes to diet, exercise or treatment.
Last reviewed on 1 October 2026. Found a mistake? Tell us.