Joules to foot-pounds converter
1 joule is 0.737562149277 foot-pounds: turn an SI energy figure into the ft·lbf found in mechanics textbooks, impact and ballistic tables and North American handbooks, using the full constant instead of a truncated one. Free in your browser.
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Run — free
Worked example
- Energy in joules
- 1
- Result
- 0.7375621493 ft·lbf
- Converted
- 0.7375621493
- Foot pounds
- 0.7375621493
- From unit
- J
A joules-to-foot-pounds converter turns an SI energy reading in joules into the imperial foot-pound force value used in mechanics textbooks, impact and ballistic tables, and many North American engineering datasheets. Approximate mental shortcuts such as one point three five six joules per foot-pound are rejected in favour of the full exact constant, so homework checks and lab exports match standard conversion tables.
Why joules and foot-pounds meet at 1.3558179483314004
The foot-pound force remains common in US customary mechanics, older ballistics notes, impact-energy ratings on fasteners and tools, and many engineering handbooks that still quote ft·lbf rather than joules. The bridge between them is exact for the international definitions: one foot is exactly zero point three zero four eight metres, and the pound-force is defined from standard gravity acting on the international pound-mass, which yields one foot-pound force equal to one point three five five eight one seven nine four eight three three one four zero zero four joules.
That makes the conversion a single exact division, foot-pounds equals joules divided by that constant, or equivalently a multiplication by the reciprocal near zero point seven three seven five six two. Teachers can contrast the exact path with a rough one-point-three-five-six rule of thumb so students see the small relative error that accumulates on large impact or spring-energy figures when the truncated constant is reused row after row.
Practical tips, checks, and related searches
Round-trip sanity checks are easy: convert one joule and confirm you receive about zero point seven three seven five six two foot-pounds after rounding, or convert one point three five five eight one seven nine four eight three three one four zero zero four joules and confirm exactly one foot-pound. If your source table quotes kilojoules or megajoules, scale to joules before calling this tool, or treat the input as already scaled only when you intentionally want raw joules.
Stay inside the absolute range so the quotient cannot overflow into a non-finite result the solver must reject. When teaching unit analysis, pair a work example such as a one-newton force through one metre with the pure energy conversion so students see that one joule is smaller than one foot-pound and that the same exact constant appears in both SI and US customary worksheets.
This landing targets people searching for joules to foot-pounds, convert J to ft-lbf, or an exact foot-pound energy calculator; it is not a multi-unit energy hub, not a foot-pounds-to-joules primary form, not a torque converter for bolt specs, and not a kinetic-energy or power calculator. Prefer this capability when the input is already in joules and you only need foot-pounds; if you must convert among many energy units in one call, use a broader energy unit converter instead.
What you can do with it
Mechanics and impact tables
Convert SI impact or spring energies in joules into ft·lbf for US customary datasheets, ballistics notes, and fastener energy ratings with the same exact factor every row.
FAQ
Is this the same as torque in foot-pounds?
Foot-pound can name either energy (work) or a moment of force. This tool converts energy in joules to energy in ft·lbf; it is not a bolt-torque calculator from N·m alone without that energy context.
Why not use 1.356 J per foot-pound?
1.356 is a rounded rule of thumb. This converter hard-codes the exact international constant 1.3558179483314004 J per ft·lbf used in precise tables and unit-conversion references.
Is the joules to foot-pounds converter free?
The browser tool is free and runs locally.
Is a joule bigger or smaller than a foot-pound?
Smaller. One foot-pound force is 1.3558179483314004 joules, so any figure in joules shrinks when you express it in foot-pounds. One joule is the work of one newton pushing through one metre.
Can I enter kilojoules or megajoules?
Not directly. The converter reads the value as plain joules, so scale a kilojoule or megajoule figure to joules first. Otherwise the result will be off by a factor of a thousand or a million.
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/conv/joules-to-foot-pounds \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"joules":1}'const res = await fetch("https://api.kit.forhosting.com/conv/joules-to-foot-pounds", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"joules": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/joules-to-foot-pounds",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"joules": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/joules-to-foot-pounds", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"joules":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"joules":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/joules-to-foot-pounds", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"joules": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.joules_to_foot_pounds",
"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.
Limits
max_abs | 1000000000000 |
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
Invalid or missing input fails with a clear invalid_input error instead of inventing a number.
Why joules and foot-pounds meet at 1.3558179483314004
The joule is the SI coherent unit of energy: one newton-metre, one watt-second, and the common reporting unit for work, heat, and stored energy in modern science.
How to call the API and what comes back
Absolute values must stay within the published limit of one trillion. Prefer bare numbers when you control the client; string numbers are accepted only when they match a strict finite numeric pattern without unit suffixes or thousand separators. Send a JSON body with one required finite number field named joules. Aliases j, J, value, energy, and joule are accepted so SDK clients and form posts can use the name that fits the product. On success the response echoes rounded joules, sets foot_pounds, result, and converted to the same rounded foot-pound magnitude, unit to the token ft·lbf, from_unit to J and to_unit to ft·lbf, factor to the rounded reciprocal multiplier near zero point seven three seven five six two, joules_per_foot_pound to one point three five five eight one seven nine four eight three three one four zero zero four, formula to the string foot_pounds equals joules divided by that constant, message to a short English summary, and steps to an ordered array of substitution lines. Failed validation—missing fields, non-finite numbers, bare plus or minus signs, non-numeric strings, values outside absolute limits, or a non-finite converted result—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, checks, and related searches
Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately omit joules or pass text.
Integration use cases
Homework and exam checks
Students convert classroom joule readings to foot-pounds and compare hand work against deterministic steps before submitting worksheets or coding kata fixtures.
Engineering unit alignment
Process notes that mix joules and foot-pounds can be normalized for SI or US customary exports, control logic, and API payloads without fragile hand-typed factor tables.
Technical questions
How many foot-pounds are in one joule?
About 0.737562149277 ft·lbf after rounding: foot_pounds = joules / 1.3558179483314004, using the exact international definition 1 ft·lbf = 1.3558179483314004 J.
What happens on invalid input?
Missing fields, non-finite values, non-numeric strings, or values outside the absolute limits return invalid_input and are never charged.