Contour Slope & Gradient Calculator
Calculate slope gradient %, angle (°), and ratio from contour lines elevation rise and horizontal run.
Last reviewed by the myCalculator Editorial Team
Input Parameters
Calculation Results
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Formula & How Contour Slope & Gradient Calculator Works
Slope is how much a surface rises for a given horizontal distance. Gradient as a percentage is (rise ÷ run) × 100 and the slope angle is arctan(rise ÷ run). A rise of 120 m over a run of 600 m is a gradient of 20%, an angle of arctan(0.2) = 11.3°. A 1 in 5 slope is the same thing. Close contour lines on a topographic map mean a steep slope and wide spacing means a gentle one. Use it for road and drive design, drainage falls, walking routes and land assessment. Note that run is the horizontal distance, not the distance along the slope, which is longer.
- Enter Elevation Change / Vertical Rise (m): Input your target parameter value.
- Enter Horizontal Ground Distance / Run (m): Input your target parameter value.
- Apply Formula: Calculate using
Gradient (%) = (Rise / Run) × 100 | Angle (θ) = arctan(Rise / Run). - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Are you using our calculation results for a university assignment, research paper, or academic report? Use the auto-generated citations below to accurately reference this tool in your bibliography.
MyCalculator.com.au. (2026). Contour Slope & Gradient Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/engineering/topographic-slope
MyCalculator.com.au. (2026) 'Contour Slope & Gradient Calculator'. Available at: https://www.mycalculator.com.au/calculators/engineering/topographic-slope (Accessed: 24 October 2026).
Frequently Asked Questions (FAQs)
How do you calculate slope gradient from contour lines?
Count the contour intervals between two points to find total elevation gain (Rise), then measure horizontal distance with a map scale (Run). Gradient % = (Rise ÷ Run) × 100.
What are Eastings and Northings?
Eastings are vertical grid lines on a topographic map (read first, moving left to right). Northings are horizontal grid lines (read second, moving bottom to top).
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
Australian Standards including AS/NZS 3000 (Wiring Rules), AS 3600 (Concrete Structures), and AS 4100 (Steel Structures).
Accreditation and technical guidelines for civil, structural, mechanical, and electrical engineering.
Dedicated Australian home loans, borrowing capacity, mortgage repayments & refinance modeling.