Energy Converter
Convert between different units of energy with step-by-step calculations.
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Quick Conversion Table
Comprehensive energy references covering nutrition, electrical, mechanical, and thermal applications
| Unit | Joules | kJ | Cal | kcal | kWh | BTU | ft⋅lb |
|---|---|---|---|---|---|---|---|
| 1 Joule | 1 | 0.001 | 0.239 | 0.000239 | 2.78e-7 | 0.000948 | 0.738 |
| 1 kJ | 1,000 | 1 | 239 | 0.239 | 0.000278 | 0.948 | 738 |
| 1 Calorie | 4.184 | 0.00418 | 1 | 0.001 | 1.16e-6 | 0.00397 | 3.09 |
| 1 kcal | 4,184 | 4.184 | 1,000 | 1 | 0.00116 | 3.97 | 3,088 |
| 1 kWh | 3,600,000 | 3,600 | 860,421 | 860 | 1 | 3,412 | 2,655,224 |
| 1 BTU | 1,055 | 1.055 | 252 | 0.252 | 0.000293 | 1 | 778 |
| 1 ft⋅lb | 1.356 | 0.00136 | 0.324 | 0.000324 | 3.77e-7 | 0.00129 | 1 |
| Real-World Applications | |||||||
| Unit | Joules | kJ | Cal | kcal | kWh | BTU | ft⋅lb |
| 🍎 Apple (80 kcal) | 334,720 | 335 | 80,000 | 80 | 0.093 | 317 | 247,040 |
| 📱 Smartphone Battery (15 Wh) | 54,000 | 54 | 12,906 | 12.9 | 0.015 | 51.2 | 39,828 |
| 🍽️ Daily Diet (2000 kcal) | 8,368,000 | 8,368 | 2,000,000 | 2,000 | 2.32 | 7,930 | 6,176,000 |
| 🏠 Home Monthly (500 kWh) | 1.8e9 | 1,800,000 | 430,210,500 | 430,211 | 500 | 1,706,000 | 1.33e9 |
| 🚗 Car Gas Tank (500 MJ) | 500,000,000 | 500,000 | 119,500,000 | 119,500 | 139 | 474,000 | 369,000,000 |
| ⚡ Lightning Strike (5 GJ) | 5e9 | 5,000,000 | 1.195e9 | 1,195,000 | 1,389 | 4,740,000 | 3.69e9 |
| 🏃 Running 1 Hour (300 kcal) | 1,255,200 | 1,255 | 300,000 | 300 | 0.349 | 1,190 | 926,400 |
| ☀️ Solar Panel Day (4 kWh) | 14,400,000 | 14,400 | 3,441,684 | 3,442 | 4 | 13,648 | 10,620,896 |
💡 Tip: The highlighted rows show key reference units - Joule (blue), kJ (green), kcal (orange), kWh (red), ft⋅lb (yellow), and lightning strike (purple) for quick reference. Bold values show when units equal themselves. Real-world applications range from nutrition to electrical consumption to natural phenomena.
Understanding Energy Conversions
A Comprehensive Guide to Energy Units and Power Measurements
Energy conversion is fundamental in physics, engineering, nutrition, and everyday life. Whether you're calculating food calories, electrical consumption, fuel efficiency, or mechanical work, understanding how to convert between different energy units is essential. This guide will help you master energy conversions across all scales and applications.
Metric System
Convert between joules, kilojoules, calories, and other metric energy units. Based on the SI system with logical relationships.
Imperial System
Work with BTU, foot-pounds, therms, and other imperial energy units. Common in US heating, cooling, and mechanical applications.
Electrical Units
Convert between kilowatt-hours, watt-hours, and other electrical energy units for power consumption and billing.
Cross-System Conversion
Convert between metric, imperial, and electrical systems. Essential for international engineering and energy management.
Food & Nutrition
Work with calories, kilocalories, and joules for nutrition labels, diet planning, and metabolic calculations.
Industrial Applications
Convert between large-scale energy units for power plants, industrial processes, and fuel consumption calculations.
Master Energy Conversions with Real Examples
Learn step-by-step how to convert between different energy units with practical examples from nutrition, electrical billing, and mechanical work
1. Metric System Conversions
Metric Conversion = Value × Power of 10
Example: 2 kilojoules to joules → 2 × 1,000 = 2,000 J
Key Relationships: 1 kJ = 1,000 J, 1 kcal = 4,184 J
Metric energy units follow decimal relationships for easy conversion
Purpose:
Converts between metric energy units using decimal factors.
“How many joules are in 2.5 kilojoules?”
Benefits:
Used in science, engineering, and most countries worldwide. Systematic decimal-based system with logical relationships.
Steps:
1. Identify the decimal factor (e.g., kJ to J is ×1,000)
2. Multiply your value by that factor
3. Add the correct unit to your result
Example: 2.5 kilojoules to joules
Calculation: 2.5 × 1,000 = 2,500
Result: 2,500 J
Result:
2.5 kilojoules = 2,500 joules
Example:
“A snack contains 100 kJ, which equals 100,000 J or about 24 kcal.”
2. Imperial System Conversions
Imperial Conversion = Value × Conversion Factor
Example: 2 BTU to foot-pounds → 2 × 778.17 = 1,556.34 ft⋅lb
Key Factors: 1 BTU = 1,055.06 J, 1 ft⋅lb = 1.356 J
Essential for US heating, cooling, and mechanical work calculations
Purpose:
Converts between imperial energy units using specific factors.
“How many foot-pounds are in 5 BTU?”
Benefits:
Common in US HVAC, mechanical engineering, and energy applications. Based on traditional energy measurements.
Steps:
1. Identify the conversion factor (e.g., BTU to ft⋅lb is ×778.17)
2. Multiply your value by the factor
3. Add the correct unit to your result
Example: 5 BTU to foot-pounds
Calculation: 5 × 778.17 = 3,890.85
Result: 3,890.85 ft⋅lb
Result:
5 BTU = 3,890.85 ft⋅lb
Example:
“A furnace rated at 80,000 BTU/hour provides about 23.4 kW of heating power.”
3. Electrical Energy Conversions
Electrical Conversion = Value × Time Factor
Example: 2 kWh to megajoules → 2 × 3.6 = 7.2 MJ
Key Factors: 1 kWh = 3.6 MJ, 1 Wh = 3,600 J
Essential for electrical billing and energy consumption calculations
Purpose:
Converts between electrical energy units for billing and consumption.
“How many megajoules are in 10 kWh?”
Benefits:
Standard for electrical billing, battery capacity, and power
Steps:
1. Identify the electrical conversion factor (e.g., kWh to MJ is ×3.6)
2. Apply the conversion factor
3. Verify with electrical standards
Example: 10 kWh to megajoules
Calculation: 10 × 3.6 = 36
Result: 36 MJ
Result:
10 kWh = 36 MJ
Example:
“A household uses 900 kWh per month, which equals 3,240 MJ of energy.”
4. Food & Nutrition Conversions
Food Energy = Value × Calorie Factor
Example: 500 kcal to kilojoules → 500 × 4.184 = 2,092 kJ
Key Factors: 1 kcal = 4.184 kJ, 1 cal = 4.184 J
Essential for nutrition labels, diet planning, and metabolism
Purpose:
Converts between food energy units for nutrition and diet.
“How many kilojoules are in 300 food calories?”
Benefits:
Essential for nutrition science, diet planning, food labeling,
Steps:
1. Identify the calorie conversion factor (e.g., kcal to kJ is ×4.184)
2. Apply the conversion factor
3. Verify with nutrition standards
Example: 300 kcal to kilojoules
Calculation: 300 × 4.184 = 1,255.2
Result: 1,255.2 kJ
Result:
300 kcal = 1,255.2 kJ
Example:
“A 2,000 kcal daily diet provides about 8,368 kJ of energy.”
Tips & Best Practices for Energy Conversions
Always check your units: kJ ↔ kcal (÷4.184), kWh ↔ MJ (×3.6)
Remember that energy = power × time, and conversions depend on exact definitions.
Use dimensional analysis: (100 kcal) × (4.184 kJ/kcal) = 418.4 kJ
Write out units to ensure they cancel correctly and avoid mistakes.
Essential Tips:
- • Memorize key conversion factors (4.184 kJ/kcal, 3.6 MJ/kWh)
- • Remember energy = force × distance for mechanical work
- • Always include units in your calculations
- • Round appropriately based on measurement precision
- • Double-check direction of conversion
Best Practices:
- • Practice with real energy values (food calories, electricity bills)
- • Use estimation to check if answers are reasonable
- • Learn both metric and imperial for versatility
- • Understand the relationship between power, energy, and time
- • Use conversion tools for complex calculations
Real-Life Applications:
- • Nutrition and diet planning
- • Electrical billing and energy consumption
- • HVAC and heating system calculations
- • Mechanical work and engine efficiency
- • Battery capacity and renewable energy
Watch Out For:
- • Confusing small calories (cal) with food calories (kcal)
- • Using approximate instead of exact factors
- • Forgetting power vs. energy distinction
- • Mixing up similar units (kJ vs kcal)
- • Not considering efficiency losses in real systems