Compare calculators
Both calculators run independently — change the inputs on either side to compare results.
Fluid Mechanics
Manning's Roughness Flow Calculator
Estimate average flow velocity in an open channel or partially-full pipe using Manning's equation with hydraulic radius, slope, and roughness coefficient. Useful for stormwater design, culvert sizing, channel design, and natural-stream hydraulic analysis.
Fill in the required fields to see your result.
Fluid Mechanics
Weir Flow Calculator
Calculate the volumetric flow rate of water passing over a weir based on weir width, upstream head, and weir type. Used by civil engineers and hydrologists to measure or control open-channel flow in rivers, canals, and water treatment plants.
Fill in the required fields to see your result.
Key differences
| Manning's Roughness Flow Calculator | Weir Flow Calculator | |
|---|---|---|
| Category | Fluid Mechanics | Fluid Mechanics |
| Inputs required | 3 | 3 |
| Result | Flow Velocity (m/s) | Flow Rate (m³/s) |
| What it does | Estimate average flow velocity in an open channel or partially-full pipe using Manning's equation with hydraulic radius, slope, and roughness coefficient. Useful for stormwater design, culvert sizing, channel design, and natural-stream hydraulic analysis. | Calculate the volumetric flow rate of water passing over a weir based on weir width, upstream head, and weir type. Used by civil engineers and hydrologists to measure or control open-channel flow in rivers, canals, and water treatment plants. |