Elevation Grade & Slope Calculator
Convert between degrees, percent slope, and rise/run ratios. Calculate elevation grade from various slope measurements instantly.
Results
Frequently Asked Questions
What is elevation grade?
Elevation grade (or slope) is the measure of the incline or slope of a surface (ground, road, slab), showing how much it rises or falls over a horizontal distance. It can be expressed as a percentage (e.g., 5% = rises 5m for every 100m) or as a ratio (e.g., 1:20 = 1m of height for every 20m of distance). It is essential for drainage (directing rainwater away from foundations), road design (defining safe slopes), accessibility (setting maximum ramp slopes), and utilities (ensuring proper sewer pipe flow).
How do you calculate elevation grade?
Elevation grade is calculated using the formula: Grade = arctan(rise/run) for degrees, or Grade % = tan(degrees) × 100 for percentage.
What is a 45 degree slope in percent?
A 45 degree slope equals exactly 100% grade (or 1:1 ratio), meaning the rise equals the run distance.
What does 1 in 5 slope mean?
A 1 in 5 slope means for every 5 units of horizontal distance, there is 1 unit of vertical rise. This equals approximately 11.31 degrees or 20% grade.
Popular Slope Conversions
| Degrees | Percent Slope | Ratio (1 in X) | |
|---|---|---|---|
| 1.00° | 1.75% | 1 in 57.29 | |
| 2.00° | 3.49% | 1 in 28.64 | |
| 3.00° | 5.24% | 1 in 19.08 | |
| 4.00° | 6.99% | 1 in 14.30 | |
| 5.00° | 8.75% | 1 in 11.43 | |
| 6.00° | 10.51% | 1 in 9.51 | |
| 7.00° | 12.28% | 1 in 8.14 | |
| 8.00° | 14.05% | 1 in 7.12 | |
| 9.00° | 15.84% | 1 in 6.31 | |
| 10.00° | 17.63% | 1 in 5.67 | |
| 15.00° | 26.79% | 1 in 3.73 | |
| 20.00° | 36.40% | 1 in 2.75 | |
| 25.00° | 46.63% | 1 in 2.14 | |
| 30.00° | 57.74% | 1 in 1.73 | |
| 35.00° | 70.02% | 1 in 1.43 | |
| 40.00° | 83.91% | 1 in 1.19 | |
| 45.00° | 100.00% | 1 in 1.00 |
How to Calculate Elevation Grade
- Enter any slope measurement: degrees, percent grade, ratio, inches per foot, or mm per meter
- The calculator instantly converts to all other slope formats
- Results show: degrees, percentage, rise/run ratio, inverse ratio, and construction measurements
Formula Reference
- Percent Grade: Grade % = tan(angle in degrees) × 100
- Rise/Run Ratio: Ratio = tan(angle in degrees)
- Angle from Percent: Degrees = arctan(percent / 100) × (180/π)
- Inches per Foot: Rise per foot = tan(degrees) × 12
Related Tools
Common Slope Examples
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- Slope (Degrees ↔ Percent) — convert grade angle to percentage
- Decimal to Percent — rise/run ratio as percentage
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