About the Power Converter
Power measures the rate at which energy is transferred or converted — how fast work is done. Engineers
move between power units constantly: a motor nameplate in horsepower, a compressor rated in tons of
refrigeration, a boiler quoted in BTU/h, and a datasheet spec in dBm all describe the same physical
quantity in different unit systems. This tool converts a single power value into every common unit at
once, so you can read across SI, imperial, thermal, CGS and telecom (logarithmic) units without doing the
arithmetic by hand.
How to Use This Converter
1. Enter a value
Type the power value you want to convert into the input field.
2. Pick its unit
Select the unit that value is currently expressed in — watts, horsepower, BTU/h, dBm, etc.
3. Read the table
The table updates instantly, showing your value converted into every other supported unit.
Power Conversion Formulas
All linear power units share a fixed multiplicative factor relative to the watt (W), the SI base unit of
power. To convert between any two linear units, this tool normalizes the input to watts first, then
converts from watts to the target unit:
P (target unit) = P (watts) ÷ factor(target unit)
The one exception is the decibel-milliwatt (dBm), a logarithmic unit referenced to 1 milliwatt, used
mainly in telecom and RF engineering:
P (dBm) = 10 × log₁₀( P (mW) / 1 mW )
P (mW) = 10 ^ ( P (dBm) / 10 )
Power Unit Conversion Factors
Quick reference for the most commonly looked-up power conversions (values shown for 1 unit):
Worked Examples
Example 1 — Motor nameplate in horsepower
A pump motor is rated at 5 hp (mechanical). In kilowatts:
5 hp × 745.6998716 W/hp = 3728.499 W ≈ 3.73 kW
Example 2 — HVAC load in tons of refrigeration
A chiller is specified at 10 tons of refrigeration. In kilowatts:
10 TR × 3516.8528 W/TR = 35 168.528 W ≈ 35.17 kW
Example 3 — RF signal strength in dBm
A wireless transmitter outputs 100 mW (0.1 W). In dBm:
10 × log₁₀(100 mW / 1 mW) = 10 × log₁₀(100) = 20 dBm
Frequently Asked Questions
What's the difference between mechanical, metric and electric horsepower?
Mechanical horsepower (hp) is defined as 550 ft·lbf/s ≈ 745.70 W and is the
imperial-system standard used for engines and motors in the US and UK. Metric horsepower (PS, from
German "Pferdestärke") is defined as 75 kgf·m/s ≈ 735.50 W and is common in European and Asian vehicle
specs. Electric horsepower is a rounded convention of exactly 746 W used historically for electric motor
ratings in the US.
Why is a ton of refrigeration a unit of power?
A ton of refrigeration describes the rate of heat absorption needed to melt
one short ton (2000 lb) of ice in 24 hours — a rate, which makes it a power unit (≈ 3516.85 W or ≈ 3.517
kW). It's still the standard way HVAC and chiller capacity is specified in the US.
Can dBm be negative?
Yes. Because dBm is a logarithmic scale referenced to 1 mW, any power below 1
mW converts to a negative dBm value (e.g. 0.001 mW ≈ -30 dBm), while any power above 1 mW is positive. A
power of exactly 1 mW is 0 dBm. dBm has no representation for zero or negative watts, since the
logarithm of a non-positive number is undefined.
What's the difference between BTU/h and BTU alone?
A BTU (British Thermal Unit) is a unit of energy, not power — it measures a
fixed amount of heat. BTU/h (or BTU/hr) is a unit of power: the rate at which that heat is delivered or
absorbed, which is what this converter uses since it's directly comparable to watts. This converter's
sibling Energy Converter (coming soon) handles BTU as a standalone energy unit.
How precise are these conversions?
This tool uses standard engineering conversion factors (e.g. exact definitions
where they exist, such as 1 hp (mechanical) = 550 ft·lbf/s, and accepted rounded constants elsewhere,
such as 1 kcal/h = 1.163 W). Results are computed in double-precision floating point and displayed with
enough decimal places for engineering use; extremely large or small values switch to scientific notation
for readability.