What does a negative grade mean?

It indicates the direction of elevation change relative to your chosen start and end points.

How is elevation difference found?

Subtract one point elevation from the other; sign gives direction and absolute value gives magnitude.

Can this result be used directly for final design?

No. CivilCalc is intended for preliminary sizing and checking; final design must follow applicable standards, authority criteria and engineering review.

Terrain Slope & Elevation Calculator

Terrain grade, elevation difference and target elevation

Terrain grade is controlled by three linked quantities: horizontal run, elevation difference (Δh) and the resulting grade. CivilCalc converts these into percent grade, 1:N ratio, slope angle and target elevation so the same calculation can support site grading, drainage direction, road profiles, utility alignments and preliminary setting-out checks.

Engineering reference updated: 19 September 2026

Core grade relationships

Grade (%) = Δh / horizontal run × 100

Δh = end elevation − start elevation. For a 1:N representation, N ≈ 100 / |grade %|.

Target elevation

Target elevation = Start elevation ± Run × Grade / 100

The sign depends on the chosen rising/falling direction. Fix the stationing direction before calculating a drainage or utility profile.

Percent grade, 1:N ratio and elevation-change reference

Grade	Approx. ratio	25 m change	50 m change	100 m change
0.5%	1:200	0.125 m	0.25 m	0.50 m
1%	1:100	0.25 m	0.50 m	1.00 m
2%	1:50	0.50 m	1.00 m	2.00 m
4%	1:25	1.00 m	2.00 m	4.00 m
5%	1:20	1.25 m	2.50 m	5.00 m

This is a geometric conversion table, not a recommended or allowable design-grade table.

Worked site-profile example

Start elevation: 102.40 m
End elevation: 100.90 m
Horizontal run: 60 m
Δh: −1.50 m
Grade: −2.50% ≈ 1:40

The alignment falls 1.50 m over 60 m. If that design grade is linear, the theoretical elevation 24 m from the start is 101.80 m.

Intermediate elevations

Two end elevations do not prove that the existing ground is a straight line. Intermediate survey points should be checked for setting-out, earthwork quantities and grading design.

0 m
102.40

15 m
102.03

30 m
101.65

45 m
101.28

60 m
100.90

Illustrative linear design profile; not a scaled long section.

Horizontal run vs slope distance

Percent grade uses horizontal run in the denominator. Using an uncorrected slope distance from field measurements can bias the result, particularly on steep ground. Reduce measured slope distance to its horizontal component where required.

Six engineering checks before using a terrain grade

1. Datum
Confirm all elevations use the same vertical datum or benchmark.

2. Direction
Fix start/end stationing and record what a negative sign means.

3. Horizontal run
Do not substitute slope distance for horizontal plan distance.

4. Intermediate points
Do not force a straight-line assumption onto irregular existing ground.

5. Survey precision
On flat grades, a small elevation error can materially change the calculated percentage.

6. Design criterion
Compare the calculated existing grade with the applicable road, drainage or utility criterion separately.

Frequently asked questions

What does a 2% grade mean?

It means 2 units of elevation change per 100 horizontal units, approximately a 1:50 ratio.

What percent grade is 1 in 200?

1/200 = 0.005, so the grade is 0.5%.

What elevation change does a 3% grade create over 50 m?

50 × 0.03 = 1.50 m of elevation change.

Is a negative grade an error?

No. It indicates falling elevation in the selected start-to-end direction; reversing the direction reverses the sign.

Are two survey points enough to describe terrain?

They define an average straight-line grade. Irregular terrain requires intermediate elevation points to describe the actual profile.

Terrain Slope and Elevation Calculator