Triangle area calculator
A triangle with a 40 ft base and a 25 ft perpendicular height covers 500 sq ft: half of base times height. Use it for triangular lots, gable walls and garden beds before ordering sod, paint or sheathing. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Base
- 40 ft
- Height
- 25
- Area
- 500 ft
- Area unit
- sqft
Triangular parcels, corner lots cut on a diagonal, and roof gable ends all reduce to the same school geometry: one base length and one perpendicular height give the area as half the product of those two measures. Survey notes, site plans, and rough framing takeoffs often list only those two numbers, not three side lengths for Heron or coordinates for the shoelace formula. This triangle area calculator accepts base and height in feet, metres, yards, inches, or centimetres, multiplies them, divides by two, and returns the area in the matching square unit so you can size sod, seed, paint, sheathing, or land value without a spreadsheet.
Why base times height over two is the right land and gable formula
Any triangle has area equal to one half base times perpendicular height, regardless of whether the triangle is right-angled, isosceles, or scalene. The base is any side you choose to call the base; the height is the perpendicular distance from that base line to the opposite vertex. For a triangular residential lot the base is often the street frontage and the height is the depth measured at right angles from the frontage line to the rear apex.
For a gable wall the base is the wall width at the eaves or plate line and the height is the vertical rise from that line to the ridge peak. The same formula covers a triangular garden bed, a pie-slice patio cut, or a triangular attic end that needs paint or housewrap. You do not need the two slanted sides unless you are ordering linear trim; area-based materials only care about the enclosed surface.
The unit field is a label only; the calculator never converts between systems, which avoids silent mix-ups when a plan is in feet and a product is sold per square metre.
What to enter and what you get back
Optional unit accepts ft, m, yd, in, or cm and defaults to ft when omitted. Dimensions below 1e-15 or above 1e12 are rejected so garbage scientific notation does not produce nonsense areas. Example: base forty feet and height twenty-five feet yields area five hundred square feet, which is the classic half of one thousand.
Pair the area with your own waste percent when ordering rolls or sheets; this capability reports clean geometric area only and does not inflate for cuts. Failed validation is not billed. The free browser path runs the identical pure function, so homework-style checks and production pipelines stay aligned.
Home projects where triangle area matters
Homeowners estimating a triangular lawn corner can multiply frontage by depth, divide by two, and feed the result into sod, seed, or fertilizer calculators without redrawing the lot in CAD. Roofers and carpenters sizing gable-end sheathing, housewrap, or exterior paint measure wall width and ridge rise, then convert area to sheets with their own waste factor. Landscapers quoting triangular beds or pie-slice hardscape get a repeatable area number for mulch, gravel, or paver coverage.
Real-estate and permit workflows sometimes need a quick parcel area when only a triangular sketch with base and height is available; a deterministic parse call is cheaper and clearer than pulling a full GIS stack. Keep requests small, pin rounded areas in tests, and you get reproducible land and material estimates for edge workers, LMS labs, and field apps without standing up geometry software of your own.
What you can do with it
Triangular lot and garden area
Enter street frontage as base and perpendicular depth as height to get square feet or square metres for sod, seed, fertilizer, or land estimates.
Gable end material takeoff
Use wall width and ridge rise as base and height to size sheathing, housewrap, or paint for a triangular gable without three-side geometry.
FAQ
How do I calculate triangle area from base and height?
Send positive numbers base and height in the same length unit.
Does height have to be perpendicular to the base?
Yes. The classic formula requires the perpendicular altitude from the base line to the opposite vertex. A slanted side length is not the height.
Can I use this for a triangular lot or gable end?
Yes. That is the intended use: lot frontage and depth, or gable wall width and ridge rise, for land and material estimates.
What if I only know three side lengths?
This calculator needs base and perpendicular height. For three sides use a Heron-formula triangle area tool instead.
Does the calculator convert feet to metres?
No. The unit you pick is only a label: enter base and height in the same unit and the area comes back in the matching square unit. That avoids silent mix-ups between a plan in feet and a product sold per square metre.
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/home/triangle-area-land \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"base":40,"height":25}'const res = await fetch("https://api.kit.forhosting.com/home/triangle-area-land", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"base": 40,
"height": 25
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/home/triangle-area-land",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"base": 40,
"height": 25
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/home/triangle-area-land", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"base":40,"height":25}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"base":40,"height":25}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/home/triangle-area-land", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"base": 40,
"height": 25
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "home.triangle_area_land",
"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
Invalid or zero dimensions fail with invalid_input and are not billed.
Why base times height over two is the right land and gable formula
This endpoint deliberately stays on base and height so takeoffs stay simple and match how plans are dimensioned. It does not solve for missing sides, angles, or Heron inputs; use a geometry solver when you only know three sides. Keep both inputs in the same length unit and read the returned area unit: feet pair with square feet, metres with square metres, and so on.
Input contract, response fields, and validation rules
POST a JSON body with two required positive finite numbers: base (aliases b, base_length, width) and height (aliases h, altitude, rise). Each length may arrive as a JSON number or as a numeric string; empty strings, non-finite values, zero, and negatives fail with invalid_input naming the field. On success the body echoes base and height rounded to twelve decimal places for stable goldens, the computed area as (base times height) divided by two with the same rounding, the unit key you chose, area_unit as the matching square label (sqft, m², sq yd, sq in, or cm²), and a formula string restating A equals base times height over two.
Integration use cases
Automation and field apps
Call the API from estimating scripts or mobile forms so crews get the same A = (base × height) / 2 result as the free browser calculator.
Technical questions
What does the triangle area calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.