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FuelForge – Calorie & Macro Calculator
Science-backed Calculator

Your Calories.
Your Rules.

Find your maintenance calories in 60 seconds using the gold-standard Mifflin-St Jeor formula — then get a personalized macro plan for your exact goal.

Start Calculating
🔬
Formula Used Mifflin-St Jeor
📊
Accuracy ±5% (Most Accurate)
Time to complete Under 60 seconds
🎯
Outputs Calories + Macros
Step 1 of 1

Enter Your Details

Fill in your stats below. All fields are required for an accurate calculation.

Personal Information

Used to calculate your Basal Metabolic Rate (BMR)

📐 Mifflin-St Jeor Formula
Please enter a valid age (15–90)
Please enter a valid height (100–250 cm)
Please enter a valid weight (30–300 kg)
Please select your activity level
Please select your goal
Your Maintenance Calories (TDEE)

0kcal/day

Based on your stats and activity level

🔥
BMR
0 kcal
🏃
Activity Multiplier
×1.55
📅
Weekly Calories
0 kcal
🔥 Fat Loss Options Calorie Deficit
😊
Mild Deficit
Gentle, sustainable pace. Least muscle loss.
–250 kcal/day
Aggressive Deficit
Faster loss, higher muscle loss risk. Short-term only.
–750 kcal/day
⚖️ Maintenance Calorie Balance
Your TDEE
⚖️
Maintenance
Eat this to stay exactly where you are in weight.
±0 kcal/day
💪 Muscle Gain Options Calorie Surplus
🚀
Aggressive Surplus
Faster muscle potential, some fat gain expected.
+500 kcal/day

Your Macro Split

Goal: 0 kcal/day
Protein
30%— g
Carbs
40%— g
Fats
30%— g
🥩
Protein
g
kcal
🌾
Carbohydrates
g
kcal
🥑
Fats
g
kcal

💡 Personalized Tips for Your Goal

Ready to Level Up? 🚀

Your calories and macros are set. Now get a free custom workout plan matched to your goal.

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Free forever
No sign-up needed
Built by coaches
The Science Behind It

What Do These Numbers Mean?

Two simple concepts power every calorie calculation. Here’s what they actually mean for you.

🔥

BMR — Basal Metabolic Rate

Your BMR is the number of calories your body burns just to stay alive — breathing, keeping your heart beating, regulating your temperature — while you’re completely at rest. Think of it as the fuel cost of simply existing.

We calculate it using the Mifflin-St Jeor formula, which is the most accurate formula for most people, validated across dozens of studies.

Male:
BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5

Female:
BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

TDEE — Total Daily Energy Expenditure

Your TDEE is the total number of calories you actually burn in a day — including your BMR plus all the movement you do: exercise, walking, even fidgeting. This is your true maintenance calorie target.

To calculate TDEE, we multiply your BMR by an activity multiplier that reflects how much you move. Eat at your TDEE and your weight stays stable.

TDEE = BMR × Activity Multiplier

To lose fat: TDEE − 250 to 750 kcal
To gain muscle: TDEE + 250 to 500 kcal

🏃 Activity Level Guide

Level Multiplier Who It’s For Weekly Exercise
Sedentary ×1.20 Desk job, little walking, no planned exercise 0 days
Lightly Active ×1.375 Office job with light daily walking or 1–3 gym sessions 1–3 days
Moderately Active ×1.55 Regular training, active lifestyle, some non-exercise movement 3–5 days
Very Active ×1.725 Daily intense training or physically demanding job 6–7 days
Extremely Active ×1.90 Elite athletes, construction workers who also train, military 2× per day

🥦 Understanding Macronutrients

Every calorie comes from one of three macronutrients. Getting the right balance is just as important as hitting your calorie target.

MacroCalories per GramMain RoleBest Sources
🥩 Protein 4 kcal/g Build & repair muscle, keep you full, support metabolism Chicken, fish, eggs, tofu, Greek yogurt
🌾 Carbohydrates 4 kcal/g Primary energy source, fuel workouts, brain function Rice, oats, potatoes, fruit, vegetables
🥑 Fats 9 kcal/g Hormones, vitamin absorption, cell health Avocado, nuts, olive oil, fatty fish

FuelForge Calculator — Built for beginners who want science, not guesswork.

Calculations are estimates based on the Mifflin-St Jeor formula. Consult a registered dietitian for personalized medical nutrition advice.

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