Calorie Calculator
Table of contents
The Calorie Calculator estimates how many calories you need per day from your sex, age, weight, height, and activity level. It can also suggest simple daily targets for maintaining, losing, or gaining weight.
What are calories and TDEE?
A calorie (kilocalorie, kcal) is a unit of energy from food. Your body spends that energy on breathing, circulation, movement, digestion, and tissue repair.
Basal Metabolic Rate (BMR) estimates what you would burn at complete rest — before intentional exercise. Total Daily Energy Expenditure (TDEE) builds on BMR by multiplying for typical daily movement and exercise. This calculator starts from BMR, applies an activity factor to approximate TDEE, then adds or subtracts calories when you select a weight-loss or weight-gain goal.
Why Mifflin-St Jeor?
The Mifflin-St Jeor equation (1990, revalidated 2005) is widely used in clinical and coaching settings to estimate resting energy needs from weight, height, age, and sex. For many adults it predicts measured BMR more closely than older equations such as Harris-Benedict. No equation is perfect — lean mass, genetics, medications, and thyroid status all matter — but Mifflin-St Jeor is a balanced default for general use.
BMR formulas used here
Weight W in kg, height H in cm, age A in years. BMR (male) = 10·W + 6.25·H − 5·A + 5 BMR (female) = 10·W + 6.25·H − 5·A − 161 These are the standard Mifflin-St Jeor forms built into this tool.
Activity multipliers
After BMR is calculated, it is multiplied by an activity factor — the same broad bands used with Harris-Benedict-style planning:
| Level | Multiplier | Typical pattern |
|---|---|---|
| Sedentary | × 1.2 | Little or no exercise; mostly seated |
| Light | × 1.375 | Light exercise 1–3 days per week |
| Moderate | × 1.55 | Moderate exercise 3–5 days per week |
| Active | × 1.725 | Hard exercise most days |
| Athlete | × 1.9 | Very hard training plus a physical job |
From maintenance to your daily target
Maintenance calories align with TDEE — roughly BMR × activity factor.
When you choose to lose or gain weight at about 0.5 kg or 1 kg per week, the tool applies a daily energy adjustment near 500 kcal or 1,000 kcal respectively. Those figures align with common clinical guidance that ties weekly mass change to sustained daily deficits or surpluses. Individual responses vary; track trends over several weeks and adjust with a professional if needed.
Macros at a glance
The gram estimates divide your calorie target using typical Acceptable Macronutrient Distribution Range thinking (roughly 30% protein, 45% carbohydrate, 25% fat). Protein and carbohydrate are counted at about 4 kcal per gram; fat at about 9 kcal per gram — standard Atwater general factors.
Athletes, therapeutic diets, or medical nutrition therapy may need different splits; treat these numbers as a starting conversation, not a prescription.
Worked examples
Example A — 30-year-old male, 75 kg, 178 cm, moderate activity, maintenance.
BMR ≈ 1,717 kcal → TDEE ≈ 2,661 kcal → daily target ≈ maintenance.
Example B — 28-year-old female, 62 kg, 165 cm, light activity, lose about 0.5 kg per week.
TDEE ≈ 1,858 kcal → daily target reduced by about 500 kcal.
Example C — 22-year-old male, 80 kg, 185 cm, athlete-level activity, gain about 0.5 kg per week.
Higher TDEE plus an added surplus yields a larger daily target.
Numbers round for display; your inputs drive the exact figures in the tool.
Why use an online calorie calculator?
- Translate height, weight, age, and sex into a BMR estimate quickly
- See how activity level changes total expenditure — often the biggest lever
- Compare maintenance calories with loss or gain targets on one screen
- Get gram targets for protein, carbs, and fat without manual arithmetic
- Run entirely in your browser — nothing is sent to a server for calculation
Important limitations
Estimated BMR and TDEE can easily differ from measured metabolism by a noticeable margin. Common reasons include:
- Activity levels are self-reported — most people pick a tier that is too high
- Muscle mass changes resting burn — two people at the same weight can differ
- Medications, stress, sleep, and illness alter expenditure
- Very low or very high body weights stretch equation accuracy
Who should use this tool?
- Adults planning nutrition around general fitness or weight management
- Anyone comparing maintenance calories with modest deficit or surplus targets
- People who want a structured starting point before consulting a dietitian
Who should seek personalised advice?
Pregnancy, breastfeeding, eating-disorder recovery, diabetes, renal disease, elite sport, or major medication changes all warrant tailored plans from qualified clinicians — not only an online estimate.
Tips for using your numbers
- Revisit your target after several weeks or after meaningful weight change
- Be conservative with activity — when unsure, choose the lower tier first
- Prioritise protein quality and overall diet pattern, not only calorie totals
- Pair calorie awareness with resistance training when losing weight
- Discuss aggressive deficits or surpluses with a healthcare provider
Frequently asked questions
How accurate is the Mifflin-St Jeor equation?
For typical adults, estimates often fall within roughly ±10% of laboratory-measured resting metabolism — better than many older population equations. Accuracy drops at extremes of body composition; athletes or people with high body fat may need methods that factor in lean mass or professional assessment.
Why does my calorie target feel too high or too low?
The activity multiplier dominates error. Desk workers who train several times a week often fit Light better than Moderate. Try one step lower for two or three weeks; if weight change matches expectations, you are closer to the right maintenance band.
Is losing about 1 kg per week safe?
A large daily deficit can be harder to sustain and may cost lean tissue. Many guidelines reserve aggressive deficits for adults with higher BMI under supervision. Closer to a healthy weight, slower loss is usually easier to maintain. Ask your clinician if you have conditions or take medications that affect diet.
Should I recalculate when my weight changes?
Yes. Every four to six weeks — or after several kilograms of change — rerun the numbers. Smaller bodies burn fewer calories at rest, so the same intake produces slower progress until you adjust.
Do protein, carb, and fat grams need to be exact?
No. The split here is a sensible default for many people. Endurance plans often emphasize carbohydrates; some therapeutic diets shift fat and carbohydrate differently. Consistency with total calories usually matters more than gram-perfect macros unless you have specific medical nutrition targets.