Torque to horsepower calculator
300 lb-ft at 5252 RPM is exactly 300 horsepower, because the formula multiplies torque by RPM and divides by 5252. Enter torque or horsepower with the engine speed and get the other figure, with the formula shown. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Rpm
- 5,252
- Torque lb ft
- 300
- Calculation mode
- torque_to_horsepower
- Horsepower
- 300
- Constant
- 5,252
This torque to horsepower calculator turns engine torque in pound-feet and rotational speed in RPM into mechanical horsepower using the familiar automotive formula HP equals torque times RPM divided by 5252. It also works backward: provide horsepower and RPM to calculate the corresponding pound-feet of torque. The result states the direction, formula, and constant, so it can be checked or recorded without guessing which convention was applied. The calculation is deterministic, requires no network service, and rejects missing, ambiguous, negative, or non-finite values instead of returning a misleading number.
How torque, RPM, and horsepower fit together
Torque describes a twisting moment, while horsepower describes the rate at which that twisting effort can do work. An engine can produce substantial torque at low speed yet make modest horsepower because the crankshaft is not completing many revolutions each minute. As RPM rises, the same pound-feet correspond to more horsepower.
For the conventional automotive units used here, the relationship is horsepower equals torque in pound-feet multiplied by RPM, then divided by 5252. The number 5252 packages the unit conversions between foot-pounds per minute, revolutions, and the definition of mechanical horsepower into a convenient rounded constant. It is also why torque and horsepower curves expressed in lb-ft and HP have equal numeric values at 5252 RPM: multiplying torque by 5252 and dividing by 5252 returns the same number.
That crossing is a unit relationship, not a rule that every engine must reach that speed or produce its peak values there. This calculator keeps the convention explicit by returning the constant and formula with every successful result, making it suitable for quick checks, worksheets, vehicle notes, and deterministic software tests.
Units, interpretation, and practical limits
The torque field is specifically pound-feet, commonly written lb-ft, and speed is revolutions per minute. Horsepower is mechanical horsepower under the standard 5252 approximation. If your torque measurement is in newton-metres, kilogram-force metres, or pound-inches, convert it to pound-feet before using this calculator; feeding another unit directly can produce a plausible-looking but incorrect answer.
The result is an ideal arithmetic conversion at the stated operating point, not an estimate of wheel horsepower, drivetrain loss, engine efficiency, acceleration, towing capacity, or fuel economy. Crankshaft and chassis dynamometers may report different power because tires, transmission, temperature correction, smoothing, and measurement procedures affect the observed data. Likewise, peak torque and peak horsepower commonly occur at different RPM values, so always pair a published torque or horsepower figure with the speed at which it applies.
Browser use is convenient for a single specification or workshop check.
What you can do with it
Check an engine specification
Combine a published lb-ft value with its stated RPM to verify the corresponding mechanical horsepower at that operating point.
Interpret a dynamometer point
Convert one torque-and-speed observation into horsepower while keeping the exact formula and conventional constant beside the result.
FAQ
Why is the constant 5252 used?
It is the conventional rounded conversion constant linking pound-feet, revolutions per minute, and mechanical horsepower.
Can I enter torque in newton-metres?
No. Convert the measurement to pound-feet first; this calculator intentionally accepts only lb-ft so units are not silently mixed.
Can I work out torque from horsepower?
Yes. Enter the horsepower and the RPM and leave torque empty: the calculator multiplies horsepower by 5252 and divides by RPM. Fill in only one of the two, never both at once.
Why do torque and horsepower curves cross at 5252 RPM?
Because at that speed the formula multiplies and divides by the same number, so lb-ft and HP read equal. It is a unit relationship, not a sign that an engine must reach that speed or peak there.
Will the result match a dyno sheet?
Not necessarily. This is an ideal conversion at one operating point, not wheel horsepower. Dynamometers report different figures because tires, transmission, temperature correction and smoothing all affect what they measure.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/travel/torque-to-horsepower \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"rpm":5252,"torque_lb_ft":300}'const res = await fetch("https://api.kit.forhosting.com/travel/torque-to-horsepower", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"rpm": 5252,
"torque_lb_ft": 300
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/travel/torque-to-horsepower",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"rpm": 5252,
"torque_lb_ft": 300
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/travel/torque-to-horsepower", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"rpm":5252,"torque_lb_ft":300}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"rpm":5252,"torque_lb_ft":300}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/travel/torque-to-horsepower", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"rpm": 5252,
"torque_lb_ft": 300
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "travel.torque_to_horsepower",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Choose the known quantity and read the result
Always provide RPM as a positive number because both directions describe output at a specific rotational speed. Then provide exactly one known quantity. Zero torque or zero horsepower is allowed and produces zero for the other quantity, but zero RPM is rejected because the inverse calculation would divide by zero and because the requested operating point would not support this conversion contract. Negative values are rejected because this page treats the inputs as output magnitudes rather than signed shaft directions. To convert torque to horsepower, send torque_lb_ft and omit horsepower; the calculator evaluates torque times RPM divided by 5252. To calculate torque from horsepower, send horsepower and omit torque_lb_ft; it rearranges the equation as horsepower times 5252 divided by RPM. The response contains mode so software can distinguish the direction, followed by torque_lb_ft, rpm, horsepower, constant, and a readable formula. Values must be finite JSON numbers or ordinary numeric strings. Do not send both horsepower and torque as an attempted consistency check: the request is deliberately rejected as ambiguous instead of silently choosing one field and ignoring the other.
Units, interpretation, and practical limits
Automated API calls cost $0.002 per successful item and use the identical pure solver, which helps importers, comparison tools, and test suites reproduce the same result without spreadsheet formulas or external services.
Integration use cases
Build vehicle comparison tools
Use a deterministic API response to normalize engine data and calculate missing torque or horsepower values in an automated workflow.
Technical questions
What formula converts torque to horsepower?
For torque in pound-feet and speed in RPM, horsepower = torque_lb_ft × RPM / 5252.
How do I calculate torque from horsepower?
Provide horsepower and RPM. The calculator uses torque_lb_ft = horsepower × 5252 / RPM.
What does the API cost?
Each successful API item costs $0.002. The browser calculator runs locally, and invalid input is rejected without a result.