Energy converter
Convert between joules (J), calories (cal), food kilocalories (kcal, often labeled Cal), kilowatt-hours (kWh), and BTU. Compare food labels (2000 kcal/day), electricity bills (kWh), and heating specs (BTU/hr inputs need time context for power).
Value
From
J
kJ
cal
kcal
Wh
kWh
BTU
To
J
kJ
cal
kcal
Wh
kWh
BTU
Result
4.18 kJ
How to convert energy units
1. Enter energy in the source unit.
2. Select target unit — watch food Cal vs small calorie (cal).
3. For electricity, kWh is energy; kW is power — do not confuse.
4. Use results for estimates; billing uses metered kWh.
Energy conversion examples
Food label
250 kcal (food) = 250 Cal = ~1,046 kJ. Small "calorie" on physics problems is 1/1000 of that.
Electricity bill
1 kWh = 3.6 MJ = 3,600,000 J. Running 1 kW heater for 1 hour consumes 1 kWh.
BTU and HVAC
10,000 BTU ≈ 10.55 MJ. Room AC ratings often in BTU/hr (power), not BTU energy alone.
When to use the energy converter
• When you compare nutrition labels in kJ (EU) vs kcal (US).
• When you translate physics homework between J and eV (if supported) or cal.
• When you relate appliance specs to electricity cost per kWh.
When to choose something else
• When you need power (watts) — energy ÷ time; use power calculators.
• When you need heating fuel volume (gallons propane) — depends on combustion efficiency.
• When you track exercise burn — estimates vary; not exact conversion issue.
Energy vs power
Energy is total work over time (kWh). Power is rate (kW). A 2 kW kettle running 0.25 hours uses 0.5 kWh. Marketing "BTU/hr" on AC is power; multiply by hours for energy if estimating daily use.
Nutrition labeling globally
US uses kcal; EU often kilojoules alongside. 1 kcal ≈ 4.184 kJ. When comparing international products, convert before judging "low energy" claims.
Frequently asked questions
Calorie vs calorie?
Food Calorie (capital C) = kilocalorie (kcal) = 1000 small calories (cal). Labels often say Cal meaning kcal.
Joules to kWh?
1 kWh = 3.6 × 10⁶ J exactly. Divide joules by 3.6e6 for kWh.
What is a BTU?
British thermal unit ≈ 1055 J. Heating/cooling industry common in US.
kWh on my bill?
Energy consumed. Multiply kWh by tariff ($/kWh) for cost.
Does converting food energy equal digestible calories?
Labels are standardized; your body absorption varies — conversion is unit math only.
Is data uploaded?
No. Conversions run locally.