# Flow Rate Calculator

Enter either the pipe diameter and velocity or the volume of fluid passing in a given time to calculate the volumetric flow rate.

## Calculate Initial Fill Volume

## Calculate Resurfacing Volume

## Calculated Flow Rate:

## On this page:

## How to Calculate Flow Rate

*Volumetric flow rate*, also referred to as *volume flow rate*, *flow rate*, or volume velocity, is defined as the volume of fluid passing a point in a given unit of time.^{[1]} The SI unit of flow rate is cubic meters per second (m³/s).

Flow rate can be found by simply measuring the amount of fluid that fills a bucket in a given amount of time or using a formula.

### Flow Rate Formula

The flow rate of a fluid can be calculated using the volumetric flow rate equation:

Q = A × v

Thus, the volume flow rate *Q* is equal to the cross-sectional area of the pipe *A* times the velocity of the fluid *v*.^{[2]}

To use the flow rate formula, substitute the cross-sectional area of the pipe and the velocity of the liquid. For a round pipe, the cross-sectional area can be found using the formula for circle area *A = πr²*.

**For example**, let’s find the flow rate for the fluid passing through a 1″ diameter pipe at a velocity of 3 feet per second.

Start by finding the cross-sectional area of the pipe.

area = π × r²

area = 3.14 × (1 ÷ 2)²

area = 3.14 × 0.25

area = 0.785398 in²

Next, it will be easier to solve later if the velocity and the area are in the same units. Convert the area in square inches to square feet by dividing by 144.

A = 0.785398 in² ÷ 144

A = 0.00545 ft²

Finally, substitute the area and velocity in the flow rate equation and solve.

Q = 0.00545 in² × 3 ft/sec

Q = 0.01635 cubic ft/sec

Thus, the flow rate is 0.01635 cubic feet per second.

### Alternate Flow Rate Formula

An alternative formula to solve flow rate is:

Q = V / t

The volume flow rate *Q* is equal to the volume of liquid passed *V* divided by the time passed *t*.

To use this formula, you need to be able to measure the volume of liquid that passes in a given time.

**For example**, let’s find the flow rate for a garden hose that can fill a 5-gallon bucket in 3 minutes.

Q = 5 / 3

Q = 1.67 gal/min

Thus, the flow rate is 1.67 gallons per minute.

Try our unit rate calculator to find the rate of other units.

## References

- Engineers Edge, Fluid Volumetric Flow Rate Equation, https://www.engineersedge.com/fluid_flow/volumeetric_flow_rate.htm
- Chris Deziel, How to Calculate Flow Rates,
*Sciencing*, https://sciencing.com/calculate-flow-rates-6199676.html