Energy Conversion Table
Convert between joules, kilojoules, calories, BTU, kilowatt-hours, electron volts, and foot-pounds with engineering-grade precision. Ideal for thermal audits, battery research, nutrition planning, power plant commissioning, and physics labs.
Built for: HVAC engineers, sustainability analysts, R&D labs, semiconductor teams, nutrition scientists, and compliance auditors who need verifiable conversions.
Type any unit name or symbol to isolate the matching row instantly. Use BTU, kWh, or eV when presenting joule to kilowatt hour conversions during audits. Clear the search to restore the full table.
Comprehensive energy conversion table normalized to 1 joule inputs.
| Unit | Symbol | Joules (J) | Calories (cal) | Kilocalories (kcal) | British Thermal Units (BTU) | Kilowatt-hours (kWh) |
|---|---|---|---|---|---|---|
| Joule | J | 1.000000e+0 | 2.390057e-1 | 2.390057e-4 | 9.478134e-4 | 2.777778e-7 |
| Kilojoule | kJ | 1.000000e+3 | 2.390057e+2 | 2.390057e-1 | 9.478134e-1 | 2.777778e-4 |
| Calorie (small) | cal | 4.184000e+0 | 1.000000e+0 | 1.000000e-3 | 3.965651e-3 | 1.162222e-6 |
| Kilocalorie | kcal | 4.184000e+3 | 1.000000e+3 | 1.000000e+0 | 3.965651e+0 | 1.162222e-3 |
| British Thermal Unit | BTU | 1.055060e+3 | 2.521654e+2 | 2.521654e-1 | 1.000000e+0 | 2.930722e-4 |
| Kilowatt-hour | kWh | 3.600000e+6 | 8.604207e+5 | 8.604207e+2 | 3.412128e+3 | 1.000000e+0 |
| Foot-pound | ft⋅lbf | 1.355820e+0 | 3.240488e-1 | 3.240488e-4 | 1.285064e-3 | 3.766167e-7 |
| Electron Volt | eV | 1.602180e-19 | 3.829302e-20 | 3.829302e-23 | 1.518568e-22 | 4.450500e-26 |
| Erg | erg | 1.000000e-7 | 2.390057e-8 | 2.390057e-11 | 9.478134e-11 | 2.777778e-14 |
💡 Click any cell to copy the factor directly into spreadsheets, lab notebooks, or ERP audit forms.
Built on International Standards
Conversion multipliers reference ISO 80000-5 definitions for thermodynamic quantities, NIST Special Publication 811, and BIPM constant updates to guarantee six-decimal precision for every unit pair.
Factors are verified annually (2025 audit complete) against calorimetry benchmarks, IEC metering specs, and DOE HVAC performance guidelines to ensure traceability for compliance reports.
✨ Feature Highlights
- ✓Comprehensive coverage of thermal, electrical, and mechanical energy units
- ✓Scientific notation output with six significant figures for clean exports
- ✓Instant search and filtering for lab or field audits
- ✓Copy-ready table cells for reports, notebooks, and ERP uploads
- ✓Responsive dark mode optimized for factory-floor tablets
- ✓Contextual tooltips explaining when BTU vs kWh delivers better clarity
📘 How to Use This Energy Conversion Table
Step 1: Identify the Source Unit
Before converting, confirm whether your dataset is logged in joules, BTU, or calories. Energy audit spreadsheets often mix electrical kWh with thermal BTU values—label each column before applying factors.
Example: An HVAC contractor receives a utility bill showing 150,000 BTU of gas consumption and 450 kWh of electricity. To compare apples-to-apples in a carbon report, they must first convert BTU to kWh using the 0.000293071 multiplier, yielding 43.96 kWh from gas.
💡 Color code spreadsheet columns by unit type—blue for electrical (kWh, J), orange for thermal (BTU, cal), green for mechanical (ft·lbf).
Step 2: Choose Precision & Significant Figures
HVAC load studies require three decimals when converting BTU to kWh, while nutrition plans can round calories at one decimal. Use the "Copy with scientific notation" toggle for physics experiments analyzing megajoules.
Step 3: Search & Filter Units
Type symbols like kWh, cal, or eV in the search box to isolate rows instantly. This is the fastest way to convert joules to kilowatt hours when presenting energy-saving scenarios to clients.
Step 4: Validate Bidirectional Accuracy
After converting kilojoules to BTU, multiply the result by the inverse factor to ensure the original value returns within tolerance. DOE Measurement & Verification (M&V) reports require ±2% accuracy.
Step 5: Export for Field Teams
Use the print/PDF button to distribute the table to facility managers, plant operators, or nutrition consultants who work offline. Highlight rows relevant to "BTU to kWh conversion for heat pumps" or "kcal to joule for dietitians."
💼 Professional Use Cases
HVAC Load Analysis
Engineers convert BTU/h to kWh when sizing chillers and calculating Seasonal Energy Efficiency Ratio (SEER). Precise joule values document savings for utility rebates.
Battery & Storage Research
Labs translate watt-hours to joules and electron volts to compare cell chemistries, discharge curves, and energy density benchmarks.
Nutrition & Metabolic Planning
Dietitians convert kilocalories to kilojoules for international food labels and metabolic studies, ensuring compliance with EU and AU labeling laws.
Industrial Steam & Process Heat
Plant operators convert BTU to foot-pounds or kilojoules when balancing boiler output, steam enthalpy, and mechanical work.
Aerospace & Propulsion
Propulsion teams translate megajoules to kilowatt-hours and BTU to foot-pounds while modeling rocket ignition energy and regenerative cooling loads.
Energy Audits & Sustainability
Consultants convert building gas BTU usage into kWh equivalents to publish unified carbon baselines and Energy Use Intensity (EUI) metrics.
Test Your Skills: Energy Conversion Challenge
Challenge yourself with our interactive conversion game!
🤯 Mind-Blowing Comparisons
Apple
A medium apple stores ~218 kJ = 52 kcal = 0.061 kWh — enough to power a phone for five hours.
AA Battery
An AA battery holds ~9,360 J = 2.6 Wh = 8.9 BTU, roughly 0.4% of a smartphone battery.
Lightning Bolt
A typical lightning bolt releases 1e9 J = 278 kWh, enough to power a house for nine days.
Falcon 9
A Falcon 9 first-stage burn expends about 1.3e13 J (3.6 million kWh), enough for 350 homes for a year.
❓ Frequently Asked Questions
How many kilowatt-hours are in one megajoule?
Divide megajoules by 3.6. Example: 12 MJ ÷ 3.6 = 3.333 kWh, the standard calculation for solar storage comparisons. This relationship is exact because 1 kWh = 3,600,000 joules = 3.6 MJ.
What is the quickest way to convert BTU to kWh for heat pump sizing?
Multiply BTU by 0.000293071. Example: 36,000 BTU/h × 0.000293071 = 10.55 kW, matching the industry rule that 12,000 BTU/h equals 3.517 kW. Mental shortcut: Divide BTU by 3,412 to approximate kW.
Why do nutrition labels use kcal while physics uses joules?
Nutrition regulations adopted kilocalories for consumer readability, whereas SI defines joule as the universal energy unit tied to the Planck constant. EU labels show both kcal and kJ.
How do I convert food Calories to kilojoules for EU packaging?
Multiply Calories (kcal) by 4.184. Example: 250 Cal × 4.184 = 1,046 kJ, rounded to 1,050 kJ per EU Regulation 1169/2011.
What causes discrepancies between different BTU conversion tables?
Some references use the International Table BTU (1,055.056 J) while others use the Thermochemical BTU (1,054.35 J). The 0.067% difference compounds in large energy audits. Default to IT BTU per NIST and ASHRAE.
Can I convert foot-pounds to joules for torque documentation?
Yes. Multiply ft·lbf by 1.35582 to obtain joules when you need to merge mechanical work data with SI-based energy reports.
How accurate is the joule to electron volt conversion?
1 eV equals 1.602176634e-19 J exactly per CODATA 2018. The 2019 SI redefinition fixed the elementary charge, so this conversion is now defined rather than measured.
When should I express energy in scientific notation?
Use scientific notation for values under 0.001 kWh or above 10^6 J to prevent rounding issues in lab notebooks and simulation exports.
How do I convert gas consumption from BTU to metric kWh for carbon reports?
Sum BTU from utility bills, multiply by 0.000293071 to get kWh, then apply the regional emissions factor (kg CO₂e/kWh). Example: 185,000,000 BTU × 0.000293071 = 54,218 kWh.
What is the relationship between kilojoules and megajoules?
1 MJ equals 1,000 kJ. Use MJ for industrial boilers or EV battery packs; kJ suits nutrition labels and lab experiments.
How do I convert BTU per hour to watts for equipment specifications?
Multiply BTU/h by 0.293071 to get watts. Example: 10,000 BTU/h = 2,931 W ≈ 3 kW. Remember: BTU = energy, BTU/h = power.
What's the difference between small calorie and large Calorie?
Small calorie (cal) heats 1 gram of water 1°C = 4.184 J. Large Calorie (Cal/kcal) heats 1 kilogram of water 1°C = 4,184 J. Food labels use large Calories.
How do I convert joules to foot-pounds for mechanical engineering drawings?
Divide joules by 1.35582 to get ft·lbf. Example: 1,000 J ÷ 1.35582 = 737.6 ft·lbf.
Can I use the same conversion factor for IT BTU and ISO BTU?
No. IT BTU (1,055.056 J) differs from Thermochemical BTU (1,054.35 J) by 0.7 J. Specify which standard you use in report headers.
How many joules in a kilowatt-hour for battery storage calculations?
1 kWh = 3,600,000 J = 3.6 MJ exactly. Example: Tesla Powerwall 13.5 kWh → 48.6 MJ.
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📞 Need Help?
Questions about energy conversions? Contact the technical support team via the in-app form or review the FAQ above. Interested in embedding the calculator? Request API documentation. Spot an error? Submit a report so the annual audit log stays current.
Last Updated: January 2025
Standards Compliance: NIST SP 811, ISO 80000-5:2019, IEC 60364-8-1
Conversion Factors Verified: 2025 Annual Audit Complete ✅