Grid Convergence Angle Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserIntermediate
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the longitude, the zone's central meridian and the latitude.
- Press Calculate.
- Read the grid convergence angle.
How it works
Estimates grid convergence — the angle between grid north and true north — as γ ≈ (longitude − central meridian) × sin(latitude).
Worked example
1° off the central meridian at −31.95°. γ ≈ −0.53° (grid north is rotated from true north).
Frequently asked questions
Why does grid convergence matter?
Bearings on a map grid differ from true bearings by the convergence angle; surveyors apply it when relating grid and true north.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.