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

Pump Power Calculator

Calculate the shaft power a pump must deliver to move fluid through a system against a given total head. Use this to size pump motors or estimate energy consumption in HVAC, water supply, and process engineering.

Flow Rate (m³/s)

Total Head (m)

Fluid Density (kg/m³)

Pump Efficiency

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.

Weir Width (m)

Head Above Weir (m)

Discharge Coefficient

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Key differences

	Pump Power Calculator	Weir Flow Calculator
Category	Fluid Mechanics	Fluid Mechanics
Inputs required	4	3
Result	Required Power (kW)	Flow Rate (m³/s)
What it does	Calculate the shaft power a pump must deliver to move fluid through a system against a given total head. Use this to size pump motors or estimate energy consumption in HVAC, water supply, and process engineering.	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.