Skip to content
Free calculators and practical guides for smarter home projects.
DIY Cost Tools

DIY Cost Tools

Circle Chord Length Calculator

Find the straight-line chord between two points on a circle from radius and the smaller central angle. The segment height, or sagitta, is the distance from the chord midpoint to the minor arc. This is different from arc length along the circle.

Enter every field in the stated units. Decimal and scientific notation are accepted for non-integer fields; blanks, commas, fractions and non-finite entries are rejected. Zero is accepted only where a field permits it.

Chord length (units)5
Minor segment height (units)0.6698729811

How to use this calculator

  1. Identify the quantities required by the model and use the field units.
  2. Replace the example values, then select Calculate or press Enter.
  3. Read the labeled outputs and check the interpretation below.

Formula and interpretation

Chord c = 2r sin(θ/2); minor segment height s = r[1−cos(θ/2)].

Calculations run in your browser. The previous results are hidden when an input changes or validation fails. This prevents an old answer from being mistaken for the new calculation. Results are displayed to approximately ten significant digits using floating-point arithmetic; that precision does not imply equal precision in measured inputs.

Worked example

Circle radius (units) = 5; Central angle (degrees) = 60. Chord length (units) = 5; Minor segment height (units) = 0.6698729811.

Substitute the example inputs into the stated formula in the same order as the labeled fields. These are the default values shown above, so the explanation and the working interface describe the same case.

Limitations

Uses central angles from 0° to 180° and an ideal circle. The angle is measured at the center, not on the circumference. Shared length units apply to radius and outputs.

This is an educational mathematical model. Check the assumptions and units for your situation. Geometry results do not establish material strength, and probability outputs do not predict an individual outcome.

Frequently asked questions

Is the chord the same as arc length?

No. A chord is straight, while an arc follows the circle; they coincide only in the zero-angle limit.

Why does the calculator reject my entry?

Each field shows its supported range. Integer fields reject fractions; mathematical conditions such as a zero divisor or invalid shape produce a separate explanation. Correct the indicated field or condition and calculate again.

How many digits should I use?

Use enough digits to retain your input accuracy. Round the final answer to the precision justified by the data; tiny residuals around theoretical zero can result from floating-point arithmetic.

Review notes and reference

Reviewed October 3, 2026. The calculator script was tested against the default example and separate boundary cases. Checks covered blank, text, comma-formatted, non-finite and out-of-range entries, plus recovery after errors. Background reference for the mathematical method. Explanations and worked examples are original.

Related calculators

Math calculators · Triangular Prism Volume Calculator · Regular Tetrahedron Calculator · Ellipsoid Volume Calculator · Search all calculators