Energy & Electricity Calculators
Calcowa's energy calculators answer the two questions that come up most around power: what a device costs to run, and how watts, volts, and amps fit together. Each one runs in your browser, shows its working, and updates live as you type. They're free, need no sign-up, and there's one below whether you're pricing an appliance or sizing a circuit.
All energy calculators
What each tool is for
The electricity cost calculator turns a device's wattage and your rate into the cost to run it per day, month, and year, with appliance presets if you don't know the watts. The watts to amps calculator works the electrical side, solving between watts, volts, and amps for DC and AC, which is what you need to size a breaker or read a nameplate.
Together they cover both halves of a power question: what it draws, and what it costs. You'll often use one and then the other when you're weighing a new appliance, since it's the draw that sets the breaker and the cost that hits the bill, and they're two sides of the same number.
Energy and power at a glance
Here are the relationships the tools lean on. They're handy for a quick check, and the calculators do the exact figure for your numbers, so you won't need to keep them memorized.
| Idea | Relationship |
|---|---|
| Power | watts = volts × amps |
| Current | amps = watts ÷ volts |
| Energy | 1 kWh = 1,000 watts for 1 hour |
| Cost | cost = kWh × rate per kWh |
| Average rate | about $0.17 per kWh in the US |
Why the numbers are worth knowing
Power and cost feel abstract until you put a number on them. Seeing that a space heater runs 38 dollars a month, or that a 1,500-watt load pulls 12.5 amps and nearly fills a 15-amp circuit, changes the choices you make. That's the point of these tools: they turn a wattage on a label into something you can act on, whether that's trimming a bill or sizing the right breaker. A few seconds of math up front saves a surprise later, and you'll make a sharper call when it's a real number rather than a guess.
Each tool keeps the inputs plain and shows the formula, so it isn't a black box. There's no sign-up and nothing to install, so the calculator you need is always a click away.
Energy calculator questions
They handle the two questions people ask most about power: what a device costs to run, and how watts, volts, and amps relate. The electricity cost calculator turns wattage and use into a dollar figure, and the watts to amps calculator solves the power formula either way. Both are free, run in your browser, and update live as you type.
Pick by the question. To price an appliance or settle what's driving the bill, use the electricity cost calculator, since it gives cost per day, month, and year. To size a circuit or breaker, or to read a label, use the watts to amps calculator, which converts between watts, volts, and amps. The grid above links both.
By the kilowatt-hour, which is a 1,000-watt load running for an hour. Your bill lists a price per kWh, usually 16 to 18 cents in the US, and your total is the energy you use times that rate. The electricity cost calculator works in those units, so you'll see exactly how a device's wattage and hours turn into dollars.
Power equals voltage times current, written P = V times I. So watts are volts times amps, amps are watts over volts, and volts are watts over amps. AC adds a power factor, and three-phase adds a square root of 3. The watts to amps calculator applies the right form once you choose your current type, so the numbers come out right.
They use the standard electrical formulas, so they're accurate for the numbers you enter. The variables are real-world: your exact rate, a device's true draw versus its label, and the power factor of an AC load. Treat the output as a solid estimate, and for a precise figure, meter the device or read the rate straight off your bill.
Yes, every one is free with no sign-up and no limit. There's nothing to install, since they run right in the page, and whatever you enter stays on your device. More tools are on the way, including solar payback and EV charging cost, but the two here already cover the everyday power and cost questions.
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