How many joules are in a calorie?

1 small calorie (cal), the physics/chemistry unit, equals 4.184 joules. This is different from the nutrition-label 'Calorie' (kcal), which equals 4,184 joules — 1,000 times larger.

What is the difference between calorie and Calorie?

A lowercase calorie (cal) is a small physics unit equal to 4.184 joules. An uppercase Calorie, also written kcal, is the nutrition label unit and equals 1,000 small calories (4,184 joules). Food energy values always use the larger Calorie/kcal.

How do I convert watts to amps?

Divide watts by voltage: Amps = Watts ÷ Volts. For example, a 1,200-watt appliance on a 120-volt US circuit draws 1,200 ÷ 120 = 10 amps. You need to know the voltage — watts alone can't convert to amps.

How many watts are in a kWh?

A kilowatt-hour isn't a direct watt equivalent — it's energy used over time. A device using 1,000 watts (1 kW) running for 1 hour uses exactly 1 kWh of energy.

How much does it cost to run a 100-watt device for a month?

At a typical rate of about $0.15 per kWh, a 100-watt device running 24 hours a day for 30 days uses 72 kWh, costing roughly $10.80. Actual cost depends on your local electricity rate and actual usage hours.

How many watts is 1 horsepower?

1 mechanical horsepower equals approximately 745.7 watts.

What voltage does my country use?

The US, Canada, and parts of Japan use around 100-120 volts for household outlets. Most of Europe, the UK, Australia, and much of Asia and Africa use around 220-240 volts.

Energy & Power Converter – Joules, Calories, kWh, Watts & Amps (Free)

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1 kWh → J 1 Calorie (kcal) → J 200 kcal → kJ 1 BTU → J

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Your converted result and a plain-English explanation will appear here.

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How It Works

Energy, Power & Current — What's the Difference?

These three quantities are related but not interchangeable without an extra piece of information.

Energy: Joules ↔ Calories

1 cal = 4.184 J · 1 kcal = 4,184 J

Nutrition labels always use kcal (written "Calorie"), never the small physics calorie.

Power × Time = Energy

1 kWh = 1 kW running for 1 hour

A kilowatt-hour is a unit of energy, not power, despite the name looking like a rate.

Power = Current × Voltage

Amps = Watts ÷ Volts

You can't convert watts to amps without knowing the voltage — they're related, not equivalent, units.

Horsepower ↔ Watts

1 hp ≈ 745.7 W

Commonly used for engines and motors.

Worked Example: A 1,200W Hair Dryer on a 120V Circuit

Amps = Watts ÷ Volts

1,200 ÷ 120 = 10 amps

✓ On a typical 15-amp US household circuit, that leaves little headroom for other devices on the same circuit.

Common Mix-Up

Calorie vs. Calorie: The 1,000x Mistake

"Calorie" means two very different amounts of energy depending on the context, and mixing them up is an easy, invisible error.

Term	Also Written	Equals	Used In
calorie (small)	cal	4.184 joules	Physics, chemistry
Calorie (large)	kcal, Cal	4,184 joules (1,000 small calories)	Nutrition labels, food energy

When a nutrition label says a snack has "200 Calories," it means 200 kcal (836,800 joules) — not 200 small calories (only 836.8 joules). Always check which one a source means before converting.

Practical Reference

What Common Appliances Cost to Run

Estimated at a typical rate of $0.15 per kWh — check your own electricity bill for your actual rate.

Appliance	Typical Power	Cost per Hour	Cost for 24h/day, 30 days
LED bulb	10 W	$0.0015	$1.08
Laptop	65 W	$0.0098	$7.02
Refrigerator	150 W (average)	$0.0225	$16.20
Window AC unit	1,000 W	$0.15	$108.00
Electric water heater	4,000 W	$0.60	$432.00

Figures are illustrative estimates only, not a guarantee of actual usage or billing. Most appliances don't run at full power 24 hours a day — use the calculator above with your own hours and rate for a more accurate estimate.

FAQ

Energy & Power Converter — Frequently Asked Questions

Common questions about energy units, power units, and electrical calculations.