Turbulent Flow Calculator

This page is designed to help determine what parameters are needed to assure a turbulent flow situation in pipes.

In the following form, at least three of the values must be provided for the calculations to work properly. If a zero (0) is put in any blank, the equation will solve for this variable. If all four values are provided, the calculator will output Reynold's number for that system.


The interior diameter of a pipe could be different than the "diameter" that the pipe is associated with. Pipes with different schedules will support different pressures, and have different interior diameters. For a table of common pipe interior diameters and schedules, see this table. The value for this calculator must be in feet.

Interior Diameter of pipe: feet

Specific Weight

The Specific Weight of the substance running through the pipes is the same as the density. For example, the Specific Weight of water at 20 C° is 62.4 lb/ft3. In this calculator, the Specific Weight needs to be in lb/ft3.

Specific Weight of substance: lb/ft3.


Viscosity is how well a substance flows. Measurements from a viscometer are normally given in centipoise. For example, the viscosity of water at 20 C° is 1.00 centipoise.

Viscosity of substance: centipoise


Velocity is how fast a the substance will travel through the pipe. In this calculator, it must be given in ft/sec, or if the flow rate is known in gallons per minute, input that value into the second box and press the convert button. The diameter must be inputted before this step is taken.

Velocity: ft/sec or gallons/minute

At least three values must be inputted before the calculations are made, otherwise the answer will be incorrect.

The following box should include the minimum value to assure turbulent flow. Keep in mind that this is a conservative measure.

If Reynold's number is given, it is a unitless number that describes the fluid flow characteristics the system. If it is above 2000, the system should have turbulent flow. Reynold's number is below 2000, the system may have laminar flow. Click here to see how to correct this situation.

This Java based calculator was developed by David Stears and Matt Stanislawski, students at the Illinois Math and Science Academy who were in a mentorship program with GCI. Their assistance is appreciated.