Sine Rule Calculator
📐 Trigonometry & Pythagoras. Use the Sine rule formula to find side a, angle a (opposite a), side b, angle b (opposite b): pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Side a | cm |
| Angle A (opposite a) | ° |
| Side b | cm |
| Angle B (opposite b) | ° |
Worked example
Find the side a when Angle A (opposite a) = 50 °, Side b = 9.04 cm, Angle B (opposite b) = 60 °.
Using a/(sin A) = b/(sin B): Side a = 7.9963 cm.
Frequently asked questions
What is the formula for Sine rule?
a/(sin A) = b/(sin B).
What do the letters stand for, and what units are used?
Side a in cm, Angle A (opposite a) in °, Side b in cm, Angle B (opposite b) in °.
How do you calculate side a?
Put the values into a/(sin A) = b/(sin B). For example, with Angle A (opposite a) = 50 °, Side b = 9.04 cm, Angle B (opposite b) = 60 °, side a = 7.9963 cm.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (side a, angle a (opposite a), side b, angle b (opposite b)) and fill in the others: it rearranges the formula for you.
