Arc Length Calculator
Solve arc length, radius, or angle for a circular arc
About this calculator
The Arc Length Calculator solves the circular-arc relation s = rθ for any one of the three quantities: the arc length from radius and angle, the radius from arc and angle, or the central angle from arc and radius. Angles work in degrees or radians and are reported in both, and the chord length 2r·sin(θ/2) is included with every result. All inputs must be positive.
How to use the Arc Length Calculator calculator
- Enter the measurements you know into the input fields.
- Read the computed properties — they update instantly as you type.
- Compare the diagram with your figure to confirm the setup is right.
- Copy the page URL to share the exact calculation.
Common examples
- r = 5, θ = 120° → arc length 10.471976, chord 8.660254
- Arc 12, θ = 90° → radius 7.639437
- r = 4, arc 6 → angle 1.5 rad = 85.943669°
- r = 10, θ = 2 rad → arc 20, chord 16.829420
Frequently asked questions
How does the Arc Length Calculator calculator work?
Enter the known measurements of your figure and the calculator applies the standard geometric formulas to find the remaining properties, alongside a diagram that reflects your numbers. All values are computed with high-precision arithmetic.
When would I use the Arc Length Calculator calculator?
It helps with geometry homework, technical drawing, construction and DIY layout, and any situation where you know some measurements of a shape and need the rest.
How accurate are the results?
Formulas are evaluated at 30 significant digits of precision internally, including roots and trigonometric functions. Displayed values are rounded for readability, but the underlying computation does not accumulate floating-point drift.
Can I share a specific calculation with someone else?
Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same figure and results for whoever clicks it.