Surveying Unit Converter

Vara (Texas) — The vara appears extensively in Spanish land grants across Texas, New Mexico, and California. The Texas vara is defined as exactly 33⅓ inches (2.7778 ft). California and other states had slightly different vara values; always check the governing jurisdiction.

Gunter's Chain— Edmund Gunter's 1620 invention became the backbone of U.S. public land surveys. One chain = 66 feet = 100 links. An acre is exactly 10 square chains. Many original metes-and-bounds descriptions in the eastern U.S. are recorded in chains and links.

Rod / Pole / Perch — All refer to the same unit: 16.5 feet. One chain = 4 rods. Found in older deeds, especially New England and the mid-Atlantic states.

Degrees-Minutes-Seconds (DMS)— The standard for U.S. land surveying. 1° = 60' = 3600". Field angles are typically recorded to the nearest second or tenth-of-a-second.

Decimal Degrees — Common in GIS software, GPS, and ALTA coordinates. Easily computed from DMS: DD = D + M/60 + S/3600.

Grads / Gons— European standard: 400 grads = 360°. Many Leica and Trimble total stations shipped to European markets default to grads. If your instrument reads 100g when you expect 90°, you're in grad mode.

Radians — Used in mathematical formulas and most programming languages. 2π rad = 360°. The horizontal curve formulas on this site all use radians internally.