Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Road Gradient Calculator

Calculates the gradient of a road or ramp as a percentage from the vertical rise and horizontal distance. Use it when designing roads, ramps, drainage channels, or checking accessibility compliance.

Horizontal Distance (m)

Vertical Rise (m)

Fill in the required fields to see your result.

Civil

Culvert Flow Calculator

Calculate the full-flow discharge capacity of a circular culvert using Manning's equation. Used by drainage engineers to check whether an existing or proposed culvert can pass a design flood without overtopping.

Culvert Diameter (inches)

Culvert Slope (%)

Manning's Roughness

Flow Depth Ratio

Fill in the required fields to see your result.

Key differences

	Road Gradient Calculator	Culvert Flow Calculator
Category	Civil	Civil
Inputs required	2	4
Result	Road Gradient (%)	Flow Rate (cfs)
What it does	Calculates the gradient of a road or ramp as a percentage from the vertical rise and horizontal distance. Use it when designing roads, ramps, drainage channels, or checking accessibility compliance.	Calculate the full-flow discharge capacity of a circular culvert using Manning's equation. Used by drainage engineers to check whether an existing or proposed culvert can pass a design flood without overtopping.