HP to ft³/s Calculator

How to Convert HP to ft³/s

The HP to ft³/s Converter calculates the flow rate in cubic feet per second (ft³/s) from horsepower (HP), efficiency, and head using the following steps:

Step 1: Convert Head to Feet (if needed):

\( \text{Head (ft)} = \text{Head (cm)} \times 0.0328084 \)
\( \text{Head (ft)} = \text{Head (m)} \times 3.28084 \)
\( \text{Head (ft)} = \text{Head (in)} \times 0.0833333 \)
\( \text{Head (ft)} = \text{Head (ft)} \times 1 \)

Step 2: Calculate GPM (Gallons per Minute):

\( \text{GPM} = \frac{\text{HP} \times 3960 \times \text{Efficiency}}{\text{Head (ft)}} \)

Step 3: Convert GPM to ft³/s (Cubic Feet per Second):

\( \text{ft³/s} = \text{GPM} \times 0.002228009 \)

Combined Formula:

\( \text{ft³/s} = \frac{\text{HP} \times 3960 \times \text{Efficiency} \times 0.002228009}{\text{Head (ft)}} \)

Where:

\( \text{HP} \): Horsepower, a unit of power.
\( \text{Efficiency} \): Pump efficiency as a decimal (e.g., 0.85 for 85%).
\( \text{Head} \): Total dynamic head in selected unit (cm, m, in, or ft), converted to feet.
\( \text{GPM} \): Gallons per minute, an intermediate flow rate unit.
\( \text{ft³/s} \): Cubic feet per second, a unit of volumetric flow rate (same as CFS).
\( 0.002228009 \): Conversion factor (1 gallon = 0.133680556 ft³, divided by 60 seconds).

Enter the horsepower, efficiency, head value, and select the head unit to calculate the flow rate in GPM and ft³/s.

Using the HP to ft³/s Converter

This converter is designed for applications in fluid dynamics, pump design, and hydraulic engineering to convert horsepower to flow rate in ft³/s (cubic feet per second).

Input the horsepower (HP), efficiency (as a decimal), head value, and select the head unit (cm, m, in, or ft). The calculator will convert the head to feet and display the flow rate in both GPM and ft³/s.

Example: Convert 2 HP to ft³/s with 0.85 efficiency and 5000 cm head.

Horsepower: \( 2 \, \text{HP} \), Efficiency: \( 0.85 \), Head: \( 5000 \, \text{cm} \)
Head in feet: \( 5000 \times 0.0328084 = 164.042 \, \text{ft} \)
GPM: \( \frac{2 \times 3960 \times 0.85}{164.042} = 41.029373 \, \text{GPM} \)
ft³/s: \( 41.029373 \times 0.002228009 = 0.091419 \, \text{ft³/s} \)
Result: \( 2 \, \text{HP} = 0.091419 \, \text{ft³/s} \)

Use this tool for accurate conversions in engineering and fluid flow calculations.

Common Conversion Table

The following table provides quick reference conversions for HP to ft³/s with Efficiency = 0.85 and Head = 50 ft (or equivalent in other units):

HP	Head	GPM	ft³/s
1	50 ft	67.32	0.149981
2	1524 cm	134.64	0.299962
5	15.24 m	336.60	0.749905
10	600 in	336.60	0.749905
20	50 ft	1346.40	2.999620

Use this table for quick lookups or to verify calculator results. Note: Head values are equivalent to 50 ft (1524 cm, 15.24 m, 600 in).

Common FAQ

Below are frequently asked questions about HP to ft³/s conversions:

Q: What is the difference between GPM and ft³/s?
A: GPM (gallons per minute) measures flow rate in gallons, while ft³/s (cubic feet per second) measures flow in cubic feet. 1 ft³/s ≈ 448.831 GPM, and 1 GPM ≈ 0.002228009 ft³/s.
Q: Why is efficiency needed in the calculation?
A: Efficiency accounts for energy losses in pumps or systems, expressed as a decimal (e.g., 0.85 for 85% efficiency).
Q: What units can I use for head?
A: You can input head in centimeters (cm), meters (m), inches (in), or feet (ft). The calculator converts all inputs to feet for computation.
Q: How accurate is this converter?
A: The converter uses the precise factor 0.002228009 (derived from 1 gallon = 0.133680556 ft³ ÷ 60) and provides results rounded to 6 decimal places for accuracy.
Q: Can negative values be used?
A: Negative HP or head values are not physically meaningful. Efficiency should be between 0 and 1. The calculator enforces positive head values.