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How to Calculate Drip Irrigation Flow

By Sarah Terry ; Updated September 21, 2017

Drip irrigation is one of the most water-efficient hydration systems used for plants. Calculating drip irrigation flow is easy and will tell you how much water flow is needed for your irrigation system. The drip-irrigation flow rate will also let you know whether you have adequate tubing and valves for the number of emitters and flow rates in each section of the system. With a simple mathematical formula, you can calculate the drip-irrigation flow rate for your entire system or a single section or zone.

Count the number of emitters in your drip irrigation system. Identify the flow rate of each emitter, which is measured in gallons per hour (GPH). If some of your emitters have a different flow rate than others, mark down the number of emitters belonging to each flow rate.

Multiply the number of emitters by the GPH to get your total drip irrigation flow rate, if all your emitters have the same GPH rate. For example, if you have 20 emitters that all have a flow rate of 2 GPH, your total drip irrigation flow rate is 40 GPH (20 emitters x 2 GPH = 40 total GPH).

Multiply the number of emitters by their respective flow rates and add the results together, if some of your emitters have different flow rates in your drip irrigation system. For instance, if you have 10 emitters with a flow rate of 2 GPH (10 emitters x 2 GPH = 20 GPH) and 10 emitters with a flow rate of 1 GPH (10 emitters x 1 GPH = 10 GPH), your total GPH for the entire drip irrigation system would be 30 GPH (20 GPH + 10 GPH = 30 total GPH).

Break down the total GPH calculation to determine the gallons per minute (GPM). Simply divide your total GPH by 60 to get your GPM rate (GPH / 60 = GPM). For example, if your total GPH is 30, your GPM rate would be 0.5 (30 GPH / 60 = 0.5 GPM).


Things You Will Need

  • Calculator


  • You can use your GPH and GPM calculations to determine the amount of water usage for your entire irrigated area. For best performance, ensure that you're using emitters with the appropriate flow rate for each type of plant. For example, flowers and vegetables usually need a dripper with a flow rate of 1 GPH, while small trees and medium-sized shrubs will need emitters with a 2 GPH flow rate.


  • Don't exceed a flow rate of 220 GPH for a single section of ½-inch poly tubing in your drip irrigation system. Also, don't exceed a 9 GPM flow rate for a ¾-inch pipe in a single zone or from a single valve.

About the Author


Sarah Terry brings over 10 years of experience writing novels, business-to-business newsletters and a plethora of how-to articles. Terry has written articles and publications for a wide range of markets and subject matters, including Medicine & Health, Eli Financial, Dartnell Publications and Eli Journals.