How this calculation works
Read a longitudinal profile as successive horizontal stations and their measured elevations. Compute each segment independently, sum ascent/descent and slope distance, then compare the endpoint grade with the largest absolute local grade.
Segment grade % = 100 × elevation change / horizontal station differenceA worked example
Stations/elevations (0,100), (20,102), (50,101) have net grade 2%. The first segment rises 2 over 20 for 10%; the second falls 1 over 30 for approximately −3.333333%.
Good to know
Horizontal chainage and a common elevation reference, not GPS positions or slope-distance chainage. Segments are straight between supplied points. No terrain outside or between the measurements is surveyed. The equal-scale plot can make small vertical changes look flat; no vertical exaggeration is applied.
Reference: NIST: exact international-foot and acre factors (opens in a new tab) ↗
Check the land-unit definitions and sources
The standard factors use the international foot and an acre of 43,560 sq ft. Cent means 1/100 acre; gunta means 1/40 acre; the selected Chennai ground means 2,400 sq ft.
The Assam report defines bigha as 14,400 sq ft, katha as 2,880 sq ft and lecha as 144 sq ft. The cited West Bengal court order mentions a 720-sq-ft katha convention. These are explicit presets, not an automatic definition for every record or every place using the same name. Match your record to the stated convention, or use its verified custom factor.
- NIST: exact international-foot and acre factors (opens in a new tab) ↗
- API Setu MDDS: acre/cent and acre/gunta relationships (opens in a new tab) ↗
- Greater Chennai Corporation: one ground is 2,400 sq ft (opens in a new tab) ↗
- Government of Assam AIRBMP framework: section 7.2, page 28 (bigha, katha and lecha) (opens in a new tab) ↗
- Supreme Court order, 7 May 2025: paragraph 2, page 2 (West Bengal katha) (opens in a new tab) ↗
The acre relationships are converted using exact base factors. Rounded or unrelated regional values in a reference table are not substituted for these definitions.
A level ending does not make every segment level
Consider stations and elevations (0,0), (10,1) and (20,0). The endpoints have the same elevation, so the net grade is zero. The two segments still have grades +10% and −10%, with one unit of recorded ascent and one unit of recorded descent. Endpoint arithmetic alone would hide the intervening rise.
A station is horizontal chainage along the selected profile, not the distance along its sloping surface. Each station difference is the horizontal run used in the denominator. Entering slope distances as stations changes that denominator and understates the magnitude of the grade.
The roof pitch calculator uses a single rise and run for a different job. This profile tool retains multiple measured sections, their signs, the steepest absolute grade and total piecewise slope distance. It does not copy one endpoint answer into every section.
Percentage grade and angle use different scales
A 100% grade means a rise equal to the horizontal run. Its angle is 45°, not 100°. A 10% grade has angle arctan(0.1), approximately 5.710593°. The table displays both so that a percentage is not mistaken for a degree measurement.
Adding a constant elevation to every point changes the elevation reference but leaves all rises, grades, ascent and distances unchanged. Changing from metres to feet also leaves grades unchanged when both stations and elevations are converted consistently.
The SVG joins the supplied points using equal horizontal and vertical scales. Small elevation differences across a long station span can look flat; the values in the table remain the quantitative reference. No peaks, depressions or terrain between measured points are inferred.
A few questions, answered
Can two points have the same station?
No. The horizontal run would be zero and an ordinary percentage grade would be undefined. Stations must increase strictly.
Can elevations be negative?
Yes. A negative elevation can be meaningful relative to your chosen reference. Keep that reference and unit consistent across every row.
Is net grade an average of the displayed percentages?
It is the run-weighted grade from first to last station, not an unweighted mean of segment percentages.