Calorie Deficit Calculator

What is a calorie deficit calculator?

A calorie deficit calculator estimates Total Daily Energy Expenditure (TDEE) from age, sex, height, weight, and activity, then shows a daily calorie target for a chosen weekly fat-loss or surplus rate. TDEE is BMR times an activity factor — not the calories you burn lying still.

This is an estimate from Mifflin-St Jeor — not medical or nutrition advice. Individual needs vary with body composition, medications, and how honestly you log activity.

How to Use the TDEE Calculator

1. Enter your personal stats: Input your age, biological sex, height, and current weight. These feed into the Mifflin-St Jeor equation, validated by the Academy of Nutrition and Dietetics as the most accurate non-lab method for estimating resting metabolic rate.
2. Select your activity level honestly: Choose the level that reflects your average week — not your best week. Most desk workers with occasional gym visits are "lightly active," not "moderately active." Overestimating here is the single most common source of calorie miscalculation.
3. Choose your goal: Select maintain, lose weight, or gain muscle. The calculator will show your TDEE maintenance number and the adjusted targets for each goal.
4. Use your maintenance number as your baseline: Eat at TDEE and your weight stays stable. Subtract 500 kcal per day for ~1 lb/week fat loss. Add 250–500 kcal for a lean bulk.

BMR vs. TDEE: What's the Difference?

• BMR (Basal Metabolic Rate): The calories your body burns at complete rest — if you stayed in bed all day and didn't move a muscle. For most adults, BMR accounts for 60–70% of total daily calorie burn.
• TDEE: Your BMR multiplied by an activity factor that accounts for everything you do — walking, workouts, standing, even digesting food. Most people's TDEE is 1.2 to 1.9× their BMR depending on lifestyle. This is the number that actually determines whether you gain, lose, or maintain weight.

Who Is This For?

• People starting a calorie-counting diet who need their actual maintenance number before they can set a meaningful deficit — guessing at 1,200 kcal when your TDEE is 2,100 means you may be in a much larger deficit than intended, or not in one at all.
• Gym-goers who've hit a plateau and suspect they've been eating at the wrong level — often they're eating at BMR rather than TDEE, leaving a phantom surplus they can't account for.
• People recovering from undereating who need to know what normal calorie intake actually looks like for their size and activity level before carefully reverse dieting back to maintenance.

Key Benefits

• Privacy. Tool inputs stay in the browser.
• Free, no account needed: Use it as many times as you want — recalculate monthly as your weight and activity change.
• No subscription, no paywall: Full results every time, nothing locked behind a sign-up.
• Maintenance, deficit, and surplus in one calculation: One run gives you all three numbers so you can make an informed decision based on your goal rather than running the math separately.

Common Use Cases

Starting a cut after years of guessing: You've been eating 1,600 kcal thinking it's a deficit, but your TDEE is actually 1,580. Running your real stats through the calculator often shows why the scale isn't moving under those inputs.

Breaking a fat loss plateau: After weeks of no scale movement, recalculate TDEE with your current (lower) weight. As you lose mass, your maintenance drops — what was a 500-calorie deficit is now 200, which explains the stall.

Reverse dieting after a long cut: If you've been in a deficit for months and want to increase calories without fat gain, your recalculated TDEE is the target to work back toward gradually over several weeks.

Common Calorie Deficit Mistakes

• Cutting too aggressively below 1,200 calories: Dropping below 1,200 kcal daily (for most adults) risks nutrient deficiencies, muscle loss, and metabolic adaptation that makes future fat loss harder — not easier.
• Not adjusting TDEE as weight drops: Every pound you lose reduces your maintenance calories. A deficit calculated at 200 lbs is no longer accurate at 185 lbs — recalculate every 4–6 weeks to keep the deficit real.
• Ignoring protein needs during a deficit: Protein is the primary lever for preserving muscle while losing fat. Most research supports 0.7–1g of protein per pound of body weight during an active deficit — not just hitting a calorie number.
• Weighing daily and reacting to single readings: Daily weight fluctuates 2–4 lbs due to water, sodium, and digestion — not fat. Track weekly averages over 3–4 weeks to see actual trend direction.

To see where your calorie target fits relative to your body composition, use the Calorie Calculator for maintenance estimates, and cross-reference your weight category with the BMI Calculator before setting an aggressive deficit floor.

Deficit targets used in this calculator are consistent with guidelines from the NIH Body Weight Planner, which models personalized calorie and activity goals based on peer-reviewed energy balance research.

Frequently Asked Questions