Convert slope distance to horizontal distance using vertical angle (HD = SD × cos VA), slope %, or elevation difference. Returns horizontal and vertical distance in feet.
Convert slope distance to horizontal distance using vertical angle, slope %, or elevation difference.
Total stations and robotic rovers perform slope reduction automatically in the field. Shop survey instruments at Express Tools.
Shop Express Tools →Slope reduction is a daily task in survey and layout work. All plan distances are horizontal — but taped measurements and many total station readings are slope distances. This calculator applies the trigonometric reduction HD = SD × cos(VA) and VD = SD × sin(VA) instantly. Use it when staking grades on a slope, checking total station distances against plan distances, or reducing tape-and-clinometer field measurements to horizontal for traverse work. The elevation difference mode is useful for GPS or level-derived vertical separations where you have the slope distance from an EDM.
Save this calculation to a Sitemark job →
Log calculations with GPS location, timestamp, and job context. Auto-generates field reports.
Start free trialSlope distance (SD) is the actual straight-line distance measured along a sloped surface or with a total station. Horizontal distance (HD) is the projected flat-ground distance between two points. HD is always less than or equal to SD. Survey plans use horizontal distances.
HD = SD × cos(vertical angle). For example, a slope distance of 100 ft measured at a 10° vertical angle gives HD = 100 × cos(10°) = 98.48 ft. Vertical distance VD = SD × sin(10°) = 17.36 ft.
Use the vertical angle from horizontal — positive for uphill shots, negative for downhill. Most total stations display vertical angle from the zenith (90° = horizontal). Subtract from 90° if your instrument shows zenith angle.
Yes. Switch to Slope % mode and enter the grade. The calculator converts slope % to a vertical angle automatically: angle = atan(slope% ÷ 100).
When you know the slope distance and the elevation difference between two points (e.g., from a level rod or GPS), use elevation difference mode. HD = √(SD² − ΔElev²).