Weight Loss Calculators
These weight loss calculators each answer one question: your energy use, your energy gap, your BMI, a kilojoule conversion, your weight loss percentage or your macros. Pick the calculator that matches your question, and the link takes you to it.
Each calculator does the arithmetic only. Outcomes vary between individuals.
Last updated: November 2026
Energy and Food Calculators
- Calorie deficit calculatorUse it to estimate the energy your body uses now and, if your BMI is 25 or more, compare it with a daily target at a healthy weight and see the gap in kJ and calories.
- BMR calculatorUse it to estimate the energy your body uses at rest, and across a day at each activity level.
- kJ to calories converterUse it to convert a food label or app figure between kilojoules and calories, in either direction.
- Macro calculator in the macros guideUse it to split a daily energy target into grams of protein, fat and carbohydrate.
Weight and Height Calculators
- BMI calculatorUse it to see your BMI, its range and the healthy weight range for your height.
- Weight loss percentage calculatorUse it to see the weight lost since your starting weight, in kilograms and as a percentage.
What Each Calculator Asks For
This table shows what to have ready. Weights go in kilograms and heights in centimetres.
| Calculator | What you enter |
|---|---|
| Calorie deficit | Sex, age, height, weight, usual activity, regular sport |
| BMR | Sex, age, weight |
| kJ to calories | Direction, one amount |
| Macros | Units, energy target, three percentages |
| BMI | Age, height, weight |
| Weight loss percentage | Starting and current weight |
What the Numbers Can and Cannot Tell You
Each calculator works from the details you enter and a published formula or range, so the result is a guide, not a diagnosis. None of the calculators measures your health directly, and none predicts how much your weight could change or by when.
A number also leaves out how you eat and move. For a healthy diet, the Australian Dietary Guidelines recommend a wide variety of nutritious foods from the five food groups every day, and limiting foods and drinks with saturated fat, added salt, added sugars and alcohol. For physical activity, the Department of Health guidelines for adults aged 18 to 64 suggest moderate to vigorous activities for 30 minutes or more on most days, plus muscle-strengthening activities on 2 or more days a week.
For the method behind the numbers, read what a calorie deficit is and how to work out yours, how many calories a day to lose weight and how to lose weight: a realistic guide. If your numbers and your weight do not seem to match, read why you may not be losing weight. For personal advice, talk to a GP or nurse practitioner, an accredited practising dietitian or another registered health practitioner.
Frequently Asked Questions
Which weight loss calculator should I use first?
It depends on your question. For a check of weight against height, start with the BMI calculator. For the energy your body uses, start with the calorie deficit calculator. Leave the macro calculator until later, because it needs a daily energy target. The calorie deficit calculator sets one if your BMI is 25 or more, and the macros guide shows another way to get one.
Should I use a BMR calculator or a calorie deficit calculator?
Use the BMR calculator if you only want to know your energy use at rest and on a usual day. Use the calorie deficit calculator if you also want a target and the gap to it. It sets a target only when your BMI is 25 or more. The calorie deficit calculator also estimates your BMR as one of its steps, but it does not show that figure.
Can a calculator predict my weight or give me a date?
No. The calculators on this page do not give a date, a timeline or a predicted weight, because outcomes vary between individuals. The weight loss percentage calculator looks backwards instead: it shows the weight lost between your starting weight and your current weight. A GP or nurse practitioner can talk through what to expect for you.
Do I need an account to use these calculators?
No. Each calculator on this page opens in your browser and shows its result without an account or a payment. You can run a calculator as many times as you like, for example with a new weight. A result is a guide, not personal medical advice, so talk to a registered health practitioner about your own numbers.
Do these calculators suit everyone?
No. The BMI calculator is for adults aged 18 and over. The BMR and calorie deficit calculators are for adults aged 19 and over, and they do not suit pregnancy or breastfeeding. The macro ranges are for otherwise healthy adults keeping their weight steady, and they are not necessarily recommendations for a weight loss diet. Each calculator page explains its own limits, including where BMI is less accurate.
References
- Eat for Health (NHMRC). Australian dietary guidelines 1 to 5. https://www.eatforhealth.gov.au/guidelines/australian-dietary-guidelines-1-5
- Australian Government Department of Health, Disability and Ageing. Recommendations for adults (18 to 64 years). https://www.health.gov.au/topics/physical-activity/24-hour-movement-guidelines-for-all-australians/recommendations-for-adults-18-to-64-years
This page is general information only and does not replace individual medical advice. Please speak with a registered Australian healthcare practitioner about your own circumstances.