Heat transfer coefficient converter
A film coefficient of 1 W/(m²·K) is 0.1761101837 BTU/(h·ft²·°F), and 1 BTU/(h·ft²·°F) is 5.6782633412 W/(m²·K). Bring imperial HVAC values, metric tables and older calorie-based references onto the same scale. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 1
- Source unit of 'value'
- W_m2_K
- To
- BTU_h_ft2_F
- Result
- 0.1761101837
- From label
- watts per square meter-kelvin
- To label
- BTU per hour square foot Fahrenheit
- Value wm2k
- 1
This heat transfer coefficient converter turns a numeric film or surface coefficient from one common engineering unit into another and returns the converted magnitude with canonical unit labels. Conversion always bridges through watts per square meter-kelvin using fixed international SI factors, so the same input always yields the same result with no network calls, no sampling, and no date-dependent shortcuts. Typical checks include one watt per square meter-kelvin to BTU per hour square foot Fahrenheit, one calorie per second square centimeter Celsius to SI, and imperial HVAC film coefficients into metric tables.
What the heat transfer coefficient converter returns and which units it understands
A heat transfer coefficient conversion answers a narrow question: given a magnitude in one unit, what is the equivalent magnitude in another unit that people actually use for convection films, surface coefficients, and simple U-value style area-based heat transfer. This calculator accepts a numeric value, a source unit, and a target unit, then returns the converted result rounded to a stable precision, the canonical from and to identifiers, human-readable labels, the intermediate value in watts per square meter-kelvin, and the SI factors used for the bridge.
Canonical ids are W_m2_K for watts per square meter-kelvin, BTU_h_ft2_F for BTU per hour square foot Fahrenheit, and cal_s_cm2_C for calories per second square centimeter Celsius. Everyday spellings such as W/(m²·K), W/m²·K, watt per square meter-kelvin, watts per square metre-kelvin, BTU/(h·ft²·°F), Btu/h·ft²·F, cal/(s·cm²·°C), and calorie per second square centimeter Celsius normalize to those ids so forms, query strings, and spreadsheets can reuse the same contract without inventing private enums.
Where heat transfer coefficient conversion fits in HVAC, process, and software
HVAC and building-physics notes often quote indoor and outdoor film coefficients in BTU per hour square foot Fahrenheit while European and ISO documentation uses watts per square meter-kelvin, so a single deterministic converter prevents hand-calculator drift when a technician, designer, or student compares convection values. CGS-era tables and some laboratory references still list calories per second square centimeter Celsius for pure research setups; aerospace and process packages may mix imperial and SI in the same heat-exchanger brief.
Teachers assign homework that needs a fast, offline check of SI to BTU film coefficients without trusting opaque apps that silently change precision. Developers call the same contract from scripts to seed deterministic test vectors for product UIs, to normalize user-entered HTCs before sizing demos, or to satisfy programming-challenge statements that demand exact factors rather than a hand-waved estimate.
Product tools use the rewrite when a learner or agent types one BTU per hour square foot Fahrenheit and the UI must show watts per square meter-kelvin and cal-scale values side by side. Pair it with thermal conductivity and heat-engine calculators when you already have surface coefficients and need conductivity or efficiency next, and with the general multi-category unit converter when the same form must also handle length or temperature.
What you can do with it
HVAC film coefficients SI ↔ imperial
Convert between W/(m²·K) and BTU/(h·ft²·°F) when comparing indoor/outdoor film coefficients across SI and US HVAC catalogs.
CGS laboratory tables to SI
Normalize cal/(s·cm²·°C) literature values into watts per square meter-kelvin for deterministic process models and modern documentation.
FAQ
What does the heat transfer coefficient converter cost?
It is free in your browser on this page.
What happens if I send an unknown unit?
Unknown or misspelled units are never silently mapped.
How are conversion factors defined?
All conversions bridge through watts per square meter-kelvin using fixed definitions: 1 BTU/(h·ft²·°F) = 5.6782633412 W/(m²·K) (IT Btu, international foot), and 1 cal/(s·cm²·°C) = 41840 W/(m²·K) (thermochemical calorie).
Does this compute heat flux or thermal conductivity?
No. This capability converts heat transfer coefficient units only. Newton cooling heat flux, wall U-value assemblies, and thermal conductivity are out of scope here.
What does a heat transfer coefficient measure?
It tells how much heat crosses each square meter of a surface for each degree of temperature difference, as with convection films, surface coefficients and simple U-value style calculations.
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/heat-transfer-coefficient \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1,"from":"W_m2_K","to":"BTU_h_ft2_F"}'const res = await fetch("https://api.kit.forhosting.com/conv/heat-transfer-coefficient", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1,
"from": "W_m2_K",
"to": "BTU_h_ft2_F"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/heat-transfer-coefficient",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1,
"from": "W_m2_K",
"to": "BTU_h_ft2_F"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/heat-transfer-coefficient", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1,"from":"W_m2_K","to":"BTU_h_ft2_F"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1,"from":"W_m2_K","to":"BTU_h_ft2_F"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/heat-transfer-coefficient", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 1,
"from": "W_m2_K",
"to": "BTU_h_ft2_F"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.heat_transfer_coefficient",
"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_value | 1000000000000000000 |
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
Supported units are watts per square meter-kelvin, BTU per hour square foot Fahrenheit, and calories per second square centimeter Celsius, plus everyday aliases such as W/(m²·K), W/m²·K, BTU/(h·ft²·°F), Btu/h·ft²·F, and cal/(s·cm²·°C).
What the heat transfer coefficient converter returns and which units it understands
There is no Nusselt correlation, no geometry model, and no wall-assembly path: the engine either multiplies and divides by fixed factors inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing value, from, or to; non-finite numbers; magnitudes above the documented ceiling; and any unit string that is not on the supported list.
How factors are defined and how results stay reproducible
Optional scientific notation on the value string is allowed when it parses as a finite decimal; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong film coefficient. Zero is a valid value and simply yields zero in the target unit. Computation multiplies value by the source factor in watts per square meter-kelvin, then divides by the target factor: one BTU per hour square foot Fahrenheit equals five point six seven eight two six three three four one two watts per square meter-kelvin using the international foot and the international table British thermal unit; one thermochemical calorie per second square centimeter Celsius equals exactly forty-one thousand eight hundred forty watts per square meter-kelvin. The preferred fields are value for the coefficient magnitude, from for the source unit, and to for the target unit, with aliases amount, h, htc, coefficient, and quantity for the value, unit, from_unit, source, and input_unit for from, and target, to_unit, output_unit, and into for to so heterogeneous clients can share one contract. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for value, result, and value_wm2k, defaulting to ten and capped at fifteen so JSON goldens stay stable. Kelvin and Celsius temperature intervals are identical, so W/(m²·°C) aliases map to the same SI id. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing unit tables yourself.
Where heat transfer coefficient conversion fits in HVAC, process, and software
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result.
Integration use cases
Homework and CI fixtures
Generate reproducible heat transfer coefficient conversions for worksheets, tutoring software, and unit tests that assert fixed SI and engineering factors.
Technical questions
Which heat transfer coefficient units are supported?
Watts per square meter-kelvin (W_m2_K), BTU per hour square foot Fahrenheit (BTU_h_ft2_F), and calories per second square centimeter Celsius (cal_s_cm2_C), including common aliases such as W/(m²·K), BTU/(h·ft²·°F), and cal/(s·cm²·°C).