KLOORAHow to Find the Area of a Triangle From Three Sides (Heron
Published 8 November 2026 by Kloora Tools
Quick answer: use the free Triangle Area Calculator (Heron) to find the area, perimeter and angles of a triangle from its three sides. It runs in your browser, so nothing you enter is uploaded or stored, and there is no signup.
What is the Triangle Area Calculator (Heron)?
Find the area, perimeter and angles of a triangle from its three sides. People often search for it as "triangle calculator", "area of a triangle from three sides" or "heron formula calculator". This free version works on any phone or computer and needs no download.
How to use the Triangle Area Calculator (Heron)
- Open the Triangle Area Calculator (Heron).
- Enter your values in the fields.
- The results update instantly as you type.
- Note or copy the numbers you need.
How it works
Heron formula: with s = (a + b + c) / 2, the area is the square root of s(s - a)(s - b)(s - c). The angles come from the law of cosines. A triangle is only valid if any two sides add up to more than the third.
Worked example
- Input: Side a: 5; Side b: 6; Side c: 7
- Result: Area: 14.696938; Perimeter: 18; Angle A: 44.4153 deg; Angle B: 57.1217 deg; Angle C: 78.463 deg; Type: Scalene
Common uses
- Measure a triangular plot of land
- Find the angles of a triangle from its sides
- Check geometry homework
Second worked example
Here is the same tool with larger numbers, so you can see how the result scales.
- Input: Side a: 7.5; Side b: 9; Side c: 10.5
- Result: Area: 33.068112; Perimeter: 27; Angle A: 44.4153 deg; Angle B: 57.1217 deg; Angle C: 78.463 deg; Type: Scalene
Tips for the best result
- Check the units and the order of the numbers before you press anything.
- Estimate the answer roughly in your head first, so you can spot an input mistake.
- Keep more decimal places during the work and round only the final answer.
- Try a simple case you already know to confirm the tool does what you expect.
Common mistakes to avoid
- Swapping two inputs, such as base and exponent or x and y.
- Using degrees where radians are expected, or the other way round.
- Rounding too early and carrying the error forward.
- Entering a percentage as a decimal, or a decimal as a percentage.
Triangle Area Calculator (Heron) compared with doing it by hand
| Triangle Area Calculator (Heron) | By hand or in a spreadsheet | |
|---|---|---|
| Speed | Instant, results update as you type | Slow, you rebuild the steps each time |
| Accuracy | Same standard method every time | Easy to slip on a formula or a unit |
| Privacy | Runs in your browser, nothing uploaded | Depends on the software you use |
| Cost | Free, no signup | Free or paid software needed |
Try it now
Open the Triangle Area Calculator (Heron) and try your own numbers or text. If it helps, share it with someone who needs it.
Frequently asked questions
What is Heron formula?
Area = the square root of s(s - a)(s - b)(s - c), where s is half the perimeter.
Why does it say the triangle is not valid?
The sum of any two sides must be greater than the third side.
What does the Triangle Area Calculator (Heron) do?
Find the area, perimeter and angles of a triangle from its three sides.
How do I use the Triangle Area Calculator (Heron)?
1. Enter your values in the fields. 2. The results update instantly as you type. 3. Note or copy the numbers you need.
Is my data safe when I use the Triangle Area Calculator (Heron)?
Yes. Everything runs in your browser on your own device. Nothing you type or choose is uploaded, stored or shared, and no AI service is used.
Does the Triangle Area Calculator (Heron) work on a phone?
Yes. It works on phones, tablets and computers in any modern browser, with nothing to install.
Do I need an account or a payment to use the Triangle Area Calculator (Heron)?
No. It is free, has no daily limit, no watermark and needs no signup.
What information does the Triangle Area Calculator (Heron) need?
You enter: Side a, Side b, Side c. The results update instantly as you change any value.
How does the Triangle Area Calculator (Heron) work?
Heron formula: with s = (a + b + c) / 2, the area is the square root of s(s - a)(s - b)(s - c).
Can I use this for "area of a triangle from three sides"?
Yes. The Triangle Area Calculator (Heron) is built for exactly that, and it also answers searches such as "triangle calculator" and "heron formula calculator".
How accurate is the Triangle Area Calculator (Heron)?
It uses the standard method and shows results to a sensible precision. For legal, medical, financial or safety decisions, confirm important numbers with a qualified professional.
Where can I find more free tools like the Triangle Area Calculator (Heron)?
Kloora Tools has over 150 free tools for CVs, PDFs, images, Urdu, calculators and everyday tasks. Browse them all from the home page.
Related free tools
More guides
Triangle Calculator App: Free, Step by Step
Triangle Calculator App free and online. Steps, answers to common questions and related searches for the Triangle Area Calculator (Heron). No signup.
7 November 2026
Pakistan Passport Size Photo Resizer (35 x 45 mm): How to Use It, Ti
Free guide to the Pakistan Passport Size Photo Resizer (35 x 45 mm). Resize a photo to the 35 x 45 mm passport size commonly used in Pakistan, and set a maxim
6 November 2026
Cron Expression Generator: How to Use It, Tips and FAQs
Free guide to the Cron Expression Generator. Build a cron schedule with simple menus and see it explained in plain English. Steps, tips and answers to common
6 November 2026