What is milliwatt?

A milliwatt is a unit of power equal to one thousandth of a watt. It is used in low-power electronics, wireless communication systems, laser specifications, and medical device power ratings.

Real-world uses

Milliwatts measure the power of laser pointers (Class 1: <1 mW; Class 3B: up to 500 mW), Bluetooth radios (typically 1–100 mW), Wi-Fi transmitters, and fibre optic signals. They are used in optical communications, consumer electronics, and medical laser specifications.

History

Milliwatts became relevant as the miniaturisation era brought small electrical and optical devices into widespread use from the mid-20th century. Consumer electronics, telecommunications, and biomedical equipment all required power specifications at this sub-watt scale.

Common mistakes

Confusing milliwatts (mW) with microwatts (µW)—1 mW = 1,000 µW. Also, assuming all laser pointers operate at the same power level; safety regulations classify lasers by output power in mW, and even small increases can be hazardous to the eyes.

What is kilocalorie per hour?

Kilocalorie per hour is a unit of power expressing energy transfer as dietary calories per hour. It is used in nutrition and exercise physiology to express the rate of energy expenditure during physical activity.

Real-world uses

Kilocalories per hour (kcal/h) are used in exercise physiology to express metabolic power output (a brisk walk burns about 300 kcal/h, cycling about 500–800 kcal/h), and in HVAC engineering in Asia and Latin America to rate heating and cooling equipment, where it bridges nutritional and thermal engineering contexts.

History

The kilocalorie per hour emerged as a natural unit at the intersection of nutritional science and physiology, where metabolic rates had long been expressed in food energy per unit time. In HVAC contexts, it provided a familiar scale for countries where kilocalories were the customary energy unit before SI adoption.

Common mistakes

Confusing kcal/h (power) with kcal (energy). A person burning 300 kcal/h for 2 hours has expended 600 kcal, not 300 kcal. Also, mixing up kcal/h with kJ/h: 1 kcal/h = 4.184 kJ/h ≈ 1.163 W.

When is this conversion used?

Converting between milliwatt and kilocalorie per hour is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.

Worked examples

1 milliwatt = 0.00085985 kilocalorie per hour

1 kilocalorie per hour = 1.163 watt

How to convert milliwatt to kilocalorie per hour

To convert milliwatt to kilocalorie per hour, multiply the value by 0.00085985.

To convert kilocalorie per hour back to milliwatt, multiply by 1,163.

Measurement standards

The watt is the SI derived unit of power, defined as one joule per second (kg·m²/s³). Horsepower remains in widespread informal use, particularly in the automotive industry, but has no single universal definition across regions.

Did you know?

The human body at rest produces about 80 watts of power — roughly enough to keep an incandescent light bulb glowing. During intense exercise, a trained cyclist can sustain over 400 watts, and elite sprinters briefly exceed 2,000 watts.

Quick reference: milliwatt to kilocalorie per hour

Common values

Available Power units

• watt conversions
• kilowatt conversions
• horsepower (mechanical) conversions
• megawatt conversions
• gigawatt conversions
• milliwatt conversions
• microwatt conversions
• BTU per hour conversions
• kilocalorie per hour conversions
• ton of refrigeration conversions

More milliwatt conversions

• Convert milliwatt to watt
• Convert milliwatt to kilowatt
• Convert milliwatt to horsepower (mechanical)
• Convert milliwatt to megawatt
• Convert milliwatt to gigawatt
• Convert milliwatt to microwatt
• Convert milliwatt to BTU per hour
• Convert milliwatt to kilocalorie per hour
• Convert milliwatt to ton of refrigeration

Assumption: horsepower values use mechanical horsepower.