How to convert 1 joule to 0.239006 calories?

1 J = 0.239006 cal (mechanical equivalent)

How to convert 1 kilowatt-hour to 3.6 megajoules?

1 kWh = 3.6 MJ (electrical energy)

How to convert 1 calorie to 4.184 joules?

1 cal = 4.184 J (thermochemical calorie)

How to convert 1 electron volt to 1.60218e-19 joules?

1 eV = 1.60218e-19 J (atomic energy)

What is the difference between energy and power?

Energy is capacity to do work (joules, kWh, kcal). Power is the rate of using energy (watts = joules per second). 1 W for 1 hour = 3,600 J = 1 Wh.

How do you convert kilowatt-hours (kWh) to joules?

Multiply kWh by 3,600,000. 1 kWh = 3.6 MJ exactly. Example: 2 kWh = 7,200,000 J. Used for electricity billing and battery capacity.

What is a 'food calorie' (kcal) versus a 'physics calorie' (cal)?

Food "Calorie" (capital C) = 1 kcal = 1,000 small calories (cal) = 4,184 J. Labels show kcal; scientific work often uses cal or J.

British Thermal Unit: heat to raise 1 pound of water by 1°F. 1 BTU ≈ 1,055 J. Used for heating and cooling capacity in the US (e.g. BTU/h).

How is energy related to work and torque?

Work = force × distance; SI unit is the joule (J = N·m). Torque has the same dimension (N·m) but is not energy — it is rotational force. Do not mix them in calculations.

How accurate is this energy converter?

Factors follow NIST/BIPM. 1 kcal = 4,184 J, 1 BTU = 1,055.06 J (IT), 1 kWh = 3.6 MJ. Results are suitable for billing, nutrition, and engineering.

Energy Converter

Electric bills are in kilowatt-hours, food labels in kilocalories, and furnace specs in BTU. One joule is the work of one newton over one meter — but nobody writes a power bill in joules. Converting between these domains avoids mix-ups when comparing diets, appliances, or fuel.

From

All Converters

Quick Reference: Most Searched Energy Conversions

1 kWh in kJBilling

3,600 kJ

1 kcal in joulesFood

4,184 J

1 BTU in kJHVAC

1.055 kJ

1000 J in calPhysics

239 cal

1 Wh in JBatteries

3,600 J

1 kJ in kcalNutrition

0.239 kcal

1 therm in kWhGas bill

29.31 kWh

1 ft⋅lbf in JMechanical

1.356 J

Real-World Energy Scale

How these numbers relate to everyday life

1.602e-19J

1 electron volt (eV)

Tiny unit for atomic and particle physics; 1 eV ≈ 1.6×10⁻¹⁹ J.

1e-7J

1 erg

CGS unit; 10 million ergs = 1 joule. Rarely used outside legacy physics.

One joule

Roughly the energy to lift a small apple 1 meter against gravity.

4.184J

1 small calorie (cal)

Heat to raise 1 g of water by 1°C. Not the same as food "Calorie".

1,055J

1 BTU

Heat to raise 1 lb of water by 1°F. US heating/cooling ratings use BTU/h.

3,600J

1 watt-hour

Energy from 1 W for 1 hour. Typical phone battery: 10–15 Wh.

4,184J

1 food calorie (kcal)

Label "Calorie" = 1 kcal = 4,184 J. Average adult needs ~2,000 kcal/day.

3,600,000J

1 kWh

Electricity billing unit. US home uses ~30 kWh/day on average.

132,000,000J

1 gallon gasoline

Approximate chemical energy; ~132 MJ. Efficiency is far lower (engine losses).

Who Uses Energy Conversions?

Nutrition & Dietetics

Food labels use kilocalories (kcal or "Cal"); research and some apps use kJ. Misreading Cal vs cal leads to a 1,000-fold error.

A 250 kcal snack = 1,046 kJ. Daily 2,000 kcal = 8,368 kJ. EU labels often show both.

Electricity Billing

Utility bills are in kWh. To compare with battery capacity (Wh) or mechanical work (J), conversion is essential.

A 0.5 kW device running 2 hours = 1 kWh = 3.6 MJ. US average residential rate ~$0.14/kWh.

HVAC & Appliances

US furnace and AC ratings use BTU/h; efficiency may be in EER or COP. European specs use watts or kWh; converting avoids undersizing.

12,000 BTU/h window AC = 3.52 kW. A 24,000 BTU/h furnace ≈ 7 kW output.

Sports Science

Treadmill displays often show kcal burned; research and power meters use joules or kilojoules. Converting helps compare studies and devices.

1 hour moderate run ~600–900 kcal = 2,500–3,800 kJ. Power meter: 200 W for 1 h = 720 kJ = 172 kcal.

Physics & Engineering

SI unit is the joule. Impact energy, strain energy, and electrical work are often in J or kJ; US engineering may still use ft⋅lbf or BTU.

1 ft⋅lbf = 1.356 J. A 100 J impact is about dropping a 10 kg mass 1 m onto an object.

Did You Know?

The "food calorie" on nutrition labels is actually a kilocalorie (1,000 small calories). When scientists say "calorie" they usually mean the small one (4.184 J); the capital-C "Calorie" in food is 4,184 J.

Source: NIST

One kWh is exactly 3.6 megajoules. It is the energy delivered by 1 kW of power for one hour — so a 100 W bulb running 10 hours uses 1 kWh.

Source: BIPM

The BTU was defined as the heat needed to raise 1 pound of water by 1°F at a specific temperature. The modern value is fixed at 1,055.06 J (IT BTU).

Source: NIST

Common Mistakes to Avoid

Confusing power (W, kW) with energy (Wh, kWh)

Power is rate; energy is total. A 2 kW heater running 30 minutes uses 1 kWh (2 × 0.5). Multiply power (kW) by time (hours) to get energy (kWh).

Using "calorie" and "Calorie" (kcal) interchangeably

1 Calorie (food) = 1 kcal = 1,000 cal = 4,184 J. A 200-calorie snack is 200 kcal = 836,800 J — not 200 small calories.

Mixing up BTU and BTU/h when sizing HVAC

BTU is energy; BTU/h is power. A "50,000 BTU" furnace usually means 50,000 BTU/h output. 50,000 BTU = 14.65 kWh of energy.

Energy Conversion Formulas

To joules (SI)

kWh to J× 3,600,000
kcal to J× 4,184
BTU to J× 1,055.06
Wh to J× 3,600

From joules

J to kcal÷ 4,184
J to kWh÷ 3,600,000
J to BTU÷ 1,055.06
J to cal÷ 4.184

SI unit is the joule (J). 1 kWh = 3.6 MJ; 1 kcal = 4,184 J (NIST).

Related Converters