Grading & Slope Calculator
Calculate cut/fill quantities, slope percentages, slope ratios, and grade break locations for site grading projects.
About this calculator
Cut (-) / Fill (+) is a straight subtraction — Proposed Elevation minus Existing Elevation — so it responds only to those two inputs; Horizontal Run and Desired Slope never enter that formula at all, no matter how far you move them. Those two inputs drive different outputs instead: Horizontal Run is the denominator in Actual Slope (the elevation difference divided by the run, times 100), so a longer run spreads the same elevation change over more distance and lowers the percent grade, while Desired Slope sets the denominator in Grade Break Distance, marking how far out the target grade intersects the existing ground.
Estimated Volume assumes a fixed 50-ft-wide swath and a simple prismoidal approximation — half the absolute elevation change times the run times that assumed width, divided by 27 for cubic yards — so it's a rough order-of-magnitude figure, not a cross-sectioned earthwork takeoff. The calculator has no concept of existing versus proposed contours between the two points, so it can't detect a grade that rises then falls within the run; it only compares the two endpoints you enter.
Inputs
Results
Cut (-) / Fill (+)
2 ft
≈ 7 credit cards
Actual Slope
2%
How to Use This Calculator
- Enter the Existing Elevation and Proposed Elevation at each end of the slope in feet.
- Set the Horizontal Run Distance in feet.
- Set Desired Slope (%) to the target grade you're comparing against — it drives Grade Break Distance, where a slope built at that percentage would reach the same elevation change.
- Read Actual Slope (%) and Slope Ratio (Run:Rise) — two equivalent ways to express the same computed grade — and compare against project specs (roads typically 1–5%, parking lots 1–2%).
- Check Cut (-) / Fill (+) to know whether material must be removed or imported.
- Use Estimated Volume in cu yd to budget earthmoving equipment and material costs.
How the result changes with Proposed Elevation
| Proposed Elevation | Cut (-) / Fill (+) | Actual Slope |
|---|---|---|
| 51 | -49 ft | 49% |
| 77 | -23 ft | 23% |
| 153 | 53 ft | 53% |
| 255 | 155 ft | 155% |
What each input means
- Existing Elevation
- Current ground elevation at the starting point.
- Proposed Elevation
- Target finished grade elevation.
- Horizontal Run
- Horizontal distance over which the grade changes.
- Desired Slope
- Target slope percentage (e.g. 2% for drainage, 33% for steep embankment).
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersExisting Elevation = 100, Proposed Elevation = 102, Horizontal Run = 100, Desired Slope = 2 = 4 input(s) provided
- Calculate Cut (-) / FillCut (-) / Fill2 = 2
- Calculate Actual SlopeActual Slope2 = 2
- Calculate Slope RatioSlope Ratio50 = 50
- Calculate Estimated VolumeEstimated Volume185.19 = 185.19
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Does the Horizontal Run affect how much cut or fill I need?
No — Cut (-) / Fill (+) is purely the Proposed Elevation minus the Existing Elevation, so it stays exactly the same no matter what you enter for Horizontal Run. Run only changes how that elevation difference gets expressed as a percent grade over distance.
Why does a longer Horizontal Run lower the Actual Slope percentage?
Because Actual Slope is the elevation difference divided by the run — spreading the same rise or drop over a longer distance produces a gentler grade. Doubling the run for a fixed elevation change exactly halves the calculated slope percentage.
How accurate is the Estimated Volume figure?
It's a rough order-of-magnitude number, not a surveyed earthwork takeoff. The formula assumes a fixed 50-foot-wide swath and a simplified prismoidal shape between the two elevation points, so real cut/fill volume from an actual cross-sectioned survey can differ substantially, especially on irregular ground.
What does Grade Break Distance tell me?
It's the distance from the start point where a slope built at your Desired Slope percentage would reach the same elevation change you're grading for — useful for locating where a new grade line meets existing ground, independent of the Actual Slope calculated from your two elevations.
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