Power Converter

Power Converter: Convert Watts, Kilowatts, Horsepower, BTU/h and dBm Instantly

A 1.5 hp pool pump, a 1,500 W space heater, a 5 kW generator, an 18,000 BTU/h mini-split, and a 30 dBm Wi-Fi radio are all rated in different units — yet every one of them describes the same physical thing: how fast energy moves. The Power Converter on Tools Hub exists to translate between those labels so you can actually compare them. Type a number, choose the unit you have and the unit you want, and the answer updates the instant you stop typing.

What makes power awkward is that no two industries agree on a unit. Electricians live in watts and kilowatts. Motor and pump catalogs cling to horsepower. HVAC techs quote BTU per hour. RF and networking engineers think in dBm and milliwatts. Scientists reach for calories per second. This converter holds all of those factors in one place, so you stop juggling a separate "watts to kilowatts" lookup, an "hp to watts" calculator, and a "dBm to watts" chart every time you cross a unit boundary.

How to Convert Power Units

There is no learning curve and no convert button to hunt for — the result is live.

1. Enter the value you already have. Decimals (1.5), large numbers (18000), and fractions of a watt all work.
2. Set the "from" unit — what your number is currently in. Reading a motor plate? That is horsepower. Reading an appliance sticker? Usually watts.
3. Set the "to" unit — what you want the answer in.
4. Read the result. It recalculates on every keystroke and every unit change.

A worked example: say a pump nameplate reads "1.5 HP" and your generator is rated in watts. Type 1.5, set "from" to horsepower and "to" to watts, and you get 1,118.5 W. Now leave the input alone and switch "to" to kilowatts — 1.12 kW — to see at a glance that a 2 kW generator clears it with margin. You never retyped the value; you just re-pointed the "to" unit.

Because the output is live, the tool doubles as a learning aid. Lock the input at 1 and cycle the "to" unit through watts, horsepower, BTU/h and dBm, and you build an instant feel for how the scales relate — something a static chart can never give you.

The Conversions People Actually Run

These are the exact lookups that send people to a power converter, each with the number this tool returns so you can sanity-check it against your own situation:

• 1,500 W → 1.5 kW. A space heater or hair dryer on a 15 A / 120 V circuit. That circuit tops out near 1,800 W, so the heater alone uses about 83% of it — add anything else and the breaker trips.
• 1 hp → ~745.7 W, and 2 hp → ~1,491 W, 1.5 hp → ~1,118 W. The motor and pump numbers that never come out round.
• 3,000 W → ~4.02 hp. Useful when a generator is sold in watts but you size equipment in horsepower.
• 5 kW → ~17,061 BTU/h. Matching an electric heater's draw to a heating capacity.
• 18,000 BTU/h → ~5.28 kW of cooling, the headline figure on a 1.5-ton mini-split.
• 30 dBm → exactly 1 W, and 20 dBm → 100 mW. The reference points every RF tech keeps in their head.
• 746 W → ~1 hp. The reverse of the classic, useful when an appliance lists watts but you are matching it to a motor sized in horsepower.

The pattern is the same each time: the alternative is a formula you half-remember or a single-purpose web result, and one transposed digit changes a buying decision or trips a breaker. Doing them all in one consistent place removes that risk.

Quick Reference: Common Power Conversions

Keep this table handy for the values that come up most often. Every figure here is what the tool returns; mechanical horsepower is used throughout.

One row worth a second look: a 1-megawatt generator equals about 1,341 horsepower. That is the kind of relationship the table makes obvious and a single-purpose lookup hides.

What Each Power Unit Actually Means

Power is the rate of energy flow — energy per unit time. The SI base unit is the watt (W): one joule per second. Every other unit below is just a different-sized or differently-anchored way of saying the same thing.

Watts, Kilowatts, Megawatts, Milliwatts

The metric family scales by thousands. One kilowatt (kW) = 1,000 W; one megawatt (MW) = 1,000 kW = 1,000,000 W; one milliwatt (mW) = 0.001 W. So converting watts to kilowatts is just kW = W ÷ 1000 — slide the decimal three places left. The mental check: 1,500 W is 1.5 kW, never 15 and never 0.15. If your answer is off by a factor of ten, you slid the decimal the wrong way.

Horsepower — and Why the Same Motor Has Two Ratings

Horsepower survives because the motor, automotive and pump trades never abandoned it. Mechanical (imperial) horsepower = 745.7 W. But there is also metric horsepower — written PS in Germany, CV in France and Italy, pk in the Netherlands — equal to 735.5 W. That 1.4% gap is exactly why a European car badged "100 PS" shows up as roughly 98.6 hp on a US spec sheet, and why the same pump can look slightly more powerful in one catalog than another. When your source is a US appliance or general motor spec, choose mechanical hp; when it is a European or Japanese vehicle figure quoted in PS or CV, choose metric. When unsure, mechanical hp is the safer default.

BTU per Hour, Calories, Foot-Pounds per Second

Heating and cooling gear is quoted in BTU per hour: about 3.412 BTU/h per watt. This is where a quick conversion pays off — a window AC rated 12,000 BTU/h is doing roughly 3.5 kW of cooling but drawing far less than that electrically, because cooling capacity and electrical draw are not the same number. Calories and kilocalories per second show up in lab work; foot-pounds per second linger in older mechanical references. All describe the same rate of energy flow, just anchored to different historical definitions of energy.

dBm — the Logarithmic Outlier

dBm is a decibel scale referenced to one milliwatt, and it is the one unit you cannot eyeball. It is logarithmic: every +3 dBm roughly doubles the power, every +10 dBm multiplies it by ten. So 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW, 30 dBm = 1 W. A device that reads 23 dBm is putting out about 200 mW, not 23 of anything linear. This non-linearity is the single biggest reason a dedicated converter matters here — get the math wrong and you are off by an order of magnitude, not a rounding error.

Edge Cases Worth Knowing

A few situations trip people up no matter which converter they use:

• Power is not energy. Watts measure rate; watt-hours and joules measure total. A 100 W bulb left on for 10 hours uses 1,000 Wh (1 kWh) of energy, but its power is always 100 W. If you are estimating an electricity bill, convert to kilowatts here, then multiply by hours and your per-kWh price separately — the Energy Converter handles the total side.
• "BTU" on a thermostat usually means BTU per hour. Air-conditioner marketing drops the "/h", but the rating is a rate. Treat a "12,000 BTU" AC as 12,000 BTU/h when you convert.
• Apparent power vs. real power. Some equipment lists volt-amps (VA) rather than watts. VA and W differ by the power factor and are not the same quantity — this converter handles true power (watts and their relatives), so convert from a watt figure when you have one.
• Motor "output" vs. "input" horsepower. A motor's nameplate hp is mechanical output; its electrical draw is higher because no motor is 100% efficient. Converting 1 hp to ~746 W gives the output, not the wattage pulled from the wall.

How Accurate Are the Results

The converter uses standard, internationally recognized factors — the same constants found in engineering handbooks and SI tables. Watt-to-kilowatt and watt-to-megawatt conversions are exact, because they are pure powers of ten. Horsepower uses mechanical hp at 745.699872 W; BTU and calorie conversions use the accepted thermochemical and international definitions; results carry enough decimal places that rounding never changes a real decision.

Crucially, every result is computed from your original input in a single step rather than by chaining approximate intermediate conversions, so you avoid the "rounding drift" that creeps in when you convert A to B by hand and then B to C. For sizing a breaker or comparing two appliances the precision is far more than you need; for scientific work the extra digits are there. If a number ever looks wrong, fall back on the two reliable gut checks: kilowatts is the watt figure with the decimal moved three places left, and one horsepower always lands near 746 watts.

Privacy

Every calculation runs in your browser. The numbers you type are used only to produce the answer on your screen — nothing is uploaded, there is no account, and no history is kept. The tool is completely free with no sign-up, no usage limit, and no watermark on anything you copy. Use it as often as you like, for personal or professional work, without sending a single figure anywhere.

Related Tools on Tools Hub

These free converters pair naturally with power conversions:

• Energy Converter — joules, kilowatt-hours and calories, for when you need total energy used rather than the rate.
• Voltage / Electrical Calculator — relate volts, amps and watts via Ohm's law for circuit and breaker sizing.
• Temperature Converter — Celsius, Fahrenheit and Kelvin, a constant companion to HVAC and heating math.
• Length Converter — meters, feet, inches and miles for project and installation planning.
• Weight Converter — kilograms, pounds, ounces and grams for shipping and engineering.
• Percentage Calculator — work out efficiency, load percentages and savings alongside your conversions.

Frequently Asked Questions

What is the difference between a power converter and a power inverter?

They are unrelated. The tool on this page is a unit converter — software that translates a number from one unit of power into another, such as watts to kilowatts or hp to watts. A physical power inverter or hardware power converter is an electrical device that changes voltage or current type, for example 12V DC to 120V AC. This tool does math, not electricity.

How do I convert watts to kilowatts?

Divide the watt figure by 1,000, or just enter your value, set "from" to watts and "to" to kilowatts. For example, 2,500 W = 2.5 kW.

How many watts are in one horsepower?

One mechanical (imperial) horsepower is approximately 745.7 W. Metric horsepower (PS / CV) is approximately 735.5 W. Pick the variant that matches your source.

How do I convert dBm to watts?

Use the formula W = 10^((dBm − 30) ÷ 10), or just select dBm as "from" and watts as "to". The shortcuts to remember: 30 dBm = 1 W, 20 dBm = 100 mW, and every +3 dBm roughly doubles the power.

Why is my kilowatt answer so small?

Kilowatts are a thousand times larger than watts, so the number shrinks when you convert up. 800 W is 0.8 kW — that small figure is correct, it is the same power in bigger units.

My result has lots of decimal places — is that a problem?

No. The extra digits are there for precision. Round to one or two places for everyday decisions; the full value is shown so scientific and engineering users are not shortchanged.

Can I convert in both directions?

Yes. The "from" and "to" menus are independent, so watts-to-horsepower and horsepower-to-watts, or kilowatts-to-BTU and BTU-to-kilowatts, are all just a matter of which unit goes where.

Which units does it support?

Watts, kilowatts, megawatts, milliwatts, mechanical and metric horsepower, BTU per hour, calories and kilocalories per second, foot-pounds per second, and dBm — covering nearly any power conversion you will meet.