🍽️Calorie Deficit Calculator
Wondering what a calorie deficit actually is? This free tool estimates your maintenance calories and explains what a deficit means relative to that — so you understand the concept clearly. An educational energy balance tool, not a weight-loss prescription.
Safe-use guidance
This is an educational tool. It shows your estimated maintenance calories and explains energy balance — it does not prescribe how many calories to eat, set weight-loss targets, or generate cutting plans. Drastic calorie restriction is not safe without medical supervision. For any real plan around nutrition or weight, please speak with a doctor or registered dietitian. If you find yourself preoccupied with restricting food or your weight, consider reaching out to a qualified professional for support.
This tool is a general reference and is not medical or dietary advice. Please consult a registered dietitian or physician before making any significant change to your diet, nutrition, or weight. Individual needs vary, and only a qualified professional can give advice tailored to you.
Free Calorie Deficit Calculator Online
Wondering what a calorie deficit actually is? Our free Calorie Deficit Calculator helps you understand it clearly. As an educational calorie deficit calculator, it first estimates your maintenance calories — the energy your body uses in a typical day — then explains what eating below that level means and how energy balance works, so you understand the concept rather than just chasing a number.
A calorie deficit simply means using more energy than you take in over time. This tool focuses on understanding: it shows your estimated maintenance calories, explains the principles behind energy balance, and highlights why slow, sustainable change matters far more than extreme restriction. It's a learning tool, not a prescription.
Enter your details to see your maintenance estimate and learn how deficits work. No sign-up, no downloads, no limits. For any real plan around your weight or nutrition, please speak with a doctor or registered dietitian. Learn more in the FAQ or About pages.
About the Calorie Deficit Calculator
Key features
Maintenance calorie estimate
Estimates your TDEE — the calories your body uses in a typical day — from height, weight, age, sex, and activity level using established formulas.
Energy balance explainer
Explains what a deficit, surplus, and balanced intake each mean relative to your maintenance estimate — focused on understanding, not prescribing.
Metric & imperial input
Switch freely between metric (cm, kg) and imperial (ft/in, lb). The calculation updates instantly without any page reload.
Two BMR formulas
Choose between Mifflin-St Jeor (the more widely used modern estimate) and Harris-Benedict (the original, historically common formula).
What a calorie deficit is
A calorie deficit occurs when you consistently take in less energy than your body uses over time. Because the body draws on stored energy to make up the shortfall, a sustained deficit is associated with weight loss. A calorie surplus — consistently consuming more than you use — is associated with weight gain. Eating at roughly your maintenance level keeps weight stable.
The size of a deficit matters a great deal. Very large or very low calorie intakes can have serious health consequences, including muscle loss, nutritional deficiencies, hormonal disruption, and disordered eating patterns. Gradual, modest changes over time are widely regarded as safer and more sustainable than aggressive restriction.
How maintenance calories are estimated
Mifflin-St Jeor (male)
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Mifflin-St Jeor (female)
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Harris-Benedict (male)
BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age
Harris-Benedict (female)
BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age
Activity multipliers
Sedentary 1.2 · Lightly active 1.375 · Moderately active 1.55 · Very active 1.725 · Extra active 1.9
Maintenance = TDEE
Maintenance calories = BMR × activity multiplier. The same formulas and multipliers used in the TDEE Calculator, so estimates are consistent across both tools.
What this tool does and doesn't do
It does: estimate your maintenance calories, show the BMR and multiplier breakdown, explain what a calorie deficit means conceptually, and present the three states of energy balance (deficit, maintenance, surplus).
It doesn't: prescribe how many calories to eat, generate a goal-weight target, suggest a specific deficit size, produce "lose X kg by [date]" projections, or include any aggressive or very-low-calorie presets.
This distinction is intentional. Personalised calorie targets involve health history, body composition, medications, and goals that no calculator can assess. A doctor or registered dietitian can account for all of those and give guidance that is actually tailored to you.
Important: this is not medical or dietary advice
Frequently Asked Questions
What is a calorie deficit?
A calorie deficit means your body uses more energy over time than it takes in from food and drink. It's a general concept in energy balance, not a specific diet.
How does this calculator work?
It estimates your maintenance calories from your height, weight, age, sex, and activity level, then explains what a deficit means relative to that maintenance level and how energy balance works, so you understand the concept rather than just chasing a number.
Will this tell me exactly how many calories to eat to lose weight?
No — and that's intentional. This is an educational tool that helps you understand the concept and see your estimated maintenance calories. It doesn't prescribe a specific intake. Individual calorie targets should be set with a doctor or registered dietitian.
What are maintenance calories?
Maintenance calories are the approximate energy your body uses in a typical day to stay at your current weight. They're estimated from your BMR (Basal Metabolic Rate) and activity level.
Why doesn't the tool suggest an aggressive deficit?
Because very large or very low calorie intakes can be unsafe and are not advisable without medical supervision. Gradual, sustainable changes are widely regarded as healthier and more effective long term.
Can I use metric or imperial units?
Yes. You can enter your details in metric (cm, kg) or imperial (ft/in, lb), and the maintenance estimate updates instantly.
How accurate is the maintenance estimate?
It's a well-established estimate, not an exact measurement. Real energy needs vary with body composition, genetics, health, and daily activity, so treat the figure as a general guide.
Is my data stored anywhere?
No. Your details are processed directly in your browser and are never stored or sent to a server, keeping your information completely private.
Does it work on mobile devices?
Yes, the tool is fully responsive and works on smartphones, tablets, and desktops without any installation.
Who should I talk to about an actual nutrition plan?
A doctor or a registered dietitian. They can account for your full health picture and give safe, personalised guidance — something no online calculator can do. If you ever find yourself preoccupied with restricting food or with your weight, consider reaching out to a qualified professional for support.