Oblique Triangle Calculator
Solve any non-right triangle from three known parts.
Enter your values
Choose one of: Two sides and the angle between (SAS), All three sides (SSS).
Enter the side a you are working with.
Enter the side b you are working with.
Enter the angle c in degrees (sas) or side c (sss) you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Side c
- 6.66634
- Angle A
- 46.237°
- Angle B
- 96.763°
- Angle C
- 37°
- Area
- 26.47986
- Perimeter
- 25.66634
- Circumradius
- 5.53853
- Inradius
- 2.06339
Quick answer
Non-right triangles are solved with the law of cosines (c² = a² + b² − 2ab·cos C) and the law of sines (a ÷ sin A = b ÷ sin B).
c² = a² + b² − 2ab·cos C
At a glance
| What it does | Solve any non-right triangle from three known parts. |
|---|---|
| Category | Math |
| Inputs needed | What do you know?, Side a, Side b, Angle C in degrees (SAS) or side c (SSS) |
| Main output | Side c |
| Formula | c² = a² + b² − 2ab·cos C |
| Cost | Free — no sign-up, no download |
How to use the Oblique Triangle Calculator
- 1Choose whether you know two sides and the included angle, or all three sides.
- 2Enter sides a and b.
- 3Enter the included angle in degrees (SAS) or the third side (SSS).
Inputs explained
- What do you know?
- Choose one of: Two sides and the angle between (SAS), All three sides (SSS).
- Side a
- Enter the side a you are working with.
- Side b
- Enter the side b you are working with.
- Angle C in degrees (SAS) or side c (SSS)
- Enter the angle c in degrees (sas) or side c (sss) you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- What do you know?Two sides and the angle between (SAS)
- Side a8
- Side b11
- Angle C in degrees (SAS) or side c (SSS)37
Results
- Side c6.66634
- Angle A46.237°
- Angle B96.763°
- Angle C37°
- Area26.47986
- Perimeter25.66634
- Circumradius5.53853
- Inradius2.06339
Frequently asked questions
What is the ambiguous case?
SSA — two sides and a non-included angle can give two valid triangles. This tool uses SAS and SSS, which are always unique.
Can I use it for right triangles?
Yes. Set the included angle to 90° and the law of cosines collapses to Pythagoras.
What do I need to enter into the Oblique Triangle Calculator?
Just 4 values: what do you know?, side a, side b, angle c in degrees (sas) or side c (sss). Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Oblique Triangle Calculator work out the answer?
Non-right triangles are solved with the law of cosines (c² = a² + b² − 2ab·cos C) and the law of sines (a ÷ sin A = b ÷ sin B). It applies the formula c² = a² + b² − 2ab·cos C and shows the working so you can check each step by hand.
Is the Oblique Triangle Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.