Free Online Calorie Deficit Calculator
Estimate your daily calorie needs with clinically validated formulas. No signup required, 100% private.
Personal Information
Settings
Your Calorie Profile
Goal-Based Adjustments
How to Use the Calculator
This tool estimates your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest — and your Total Daily Energy Expenditure (TDEE), which factors in your activity level. Follow these steps. For a deeper dive into the math, read our complete guide on calculating your TDEE and BMR.
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Select Unit System: Choose between Metric (kg, cm), US (lb, ft/in), or Imperial (lb, cm) at the top of the calculator.
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Enter Personal Info: Input your age, select your gender, and enter your height and weight.
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Set Activity Level: Choose the option that best represents your daily exercise and work habits to calculate your TDEE.
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Adjust Settings (Optional): Under "Settings", select your preferred BMR formula. If you choose "Katch-McArdle," a new field will appear asking for your Body Fat Percentage (you can find this using our body fat calculator).
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Calculate: Click the "Calculate Calories" button to view your BMR, TDEE, and goal-based adjustments for weight loss or muscle gain.
BMR Equations
Female: BMR = 10 × W + 6.25 × H − 5 × A − 161
W = weight (kg), H = height (cm), A = age (years)
Published in 1990, this is considered the most accurate formula for estimating BMR in the general population. It tends to be more accurate than Harris-Benedict for overweight and obese individuals.
Female: BMR = 447.593 + 9.247 × W + 3.098 × H − 4.330 × A
Originally published in 1919 and revised by Roza and Shizgal in 1984. Historically the most widely used BMR formula, though it can overestimate by ~5% for obese individuals compared to Mifflin-St Jeor.
LBM = W × (1 − BF / 100)
W = weight (kg), BF = body fat %, LBM = lean body mass (kg)
Unlike the other formulas, Katch-McArdle accounts for lean body mass rather than total body weight, making it more accurate for individuals who know their body fat percentage (which you can measure with our body fat calculator). It is gender-independent.
Food Energy Converter
Convert between common food energy units used on nutrition labels worldwide. The large Calorie (Cal or kcal) is the standard on most food packaging. Kilojoules (kJ) are used in Australia, New Zealand, Europe, and many other regions. Enter a value and select units to convert instantly.
| Unit | Equivalent | Region / Use |
|---|---|---|
| 1 kcal | 4.184 kJ | US, Canada, most labels |
| 1 kJ | 0.2390 kcal | EU, Australia, NZ |
| 1 cal (thermo) | 4.184 J | Scientific use (small cal) |
| 1 Wh | 0.8604 kcal | Electrical energy context |
| 1 BTU (th) | 0.2522 kcal | Heating / HVAC context |
Frequently Asked Questions (FAQ)
What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body burns (your TDEE). When your body doesn't have enough calories from food to meet its energy needs, it starts breaking down stored fat for energy, resulting in weight loss over time. If you prefer a low-carb approach to dieting, you might also like our keto macro calculator.
Which BMR formula is the most accurate?
The Mifflin-St Jeor equation is generally considered the most accurate formula for the general population today. However, if you know your exact body fat percentage (which you can find using our body fat calculator), the Katch-McArdle formula is often more accurate because it relies on lean body mass rather than total body weight.
How large should my calorie deficit be?
A standard and safe calorie deficit for sustainable weight loss is about 500 calories per day, which typically results in losing about 1 pound (0.5 kg) per week. To see how this weight loss affects your overall body mass, you can use our BMI calculator. Larger deficits can lead to faster weight loss but may cause muscle loss, nutrient deficiencies, and fatigue. To learn more, read our guide on how many calories you should eat to lose weight.
Is it safe to eat below my BMR?
Eating below your BMR is generally not recommended without medical supervision. Your BMR represents the energy your body needs just to keep your organs functioning while at rest. Consistently eating below this number can slow down your metabolism and lead to health complications.
Why is my TDEE higher than my BMR?
Your BMR is the energy burned doing absolutely nothing (like lying in bed all day). Your TDEE is your BMR plus the calories you burn through daily activities, exercise, and digesting food. Unless you are in a coma, your TDEE will always be higher than your BMR.
Does this calculator save my health data?
No. This is a privacy-first tool. All calculations are performed directly in your browser. We do not collect, store, or transmit your age, weight, or any other personal information.