Enter the total number of people in a giver area into the calculator to determine the average daily water demand, maximum day demand, and peak hour demand.

Water Demand Formula

The following equation is used to calculate the Water Demand.

ADWD = (225 * P) + (225*P*.10)

  • Where ADD is the average daily water demand (L/day)
  • P is the size of the population

ADD = ADWD / 86,400

MDD = 1.44 * ADD

PHD = 2.3 * ADD

  • Where MDD is the maximum daily water demand (L/s)
  • ADD is the average daily water demand (L/s)
  • PHD is the peak daily water demand (L/S)

What is a Water Demand?


Water demand is defined as the total water usage of an area per unit of time. Typically, water demand is calculated in terms of daily usage, or average usage per second (L/s)

How to Calculate Water Demand?

Example Problem:

The following example outlines the steps and information needed to calculate Water Demand.

First, determine the size of the population. In this example, we are looking at a city of 100,000 residents.

Next, use the formula above to calculate the average daily water usage.

ADWD = (225 * 100,000) + (225*100,000*.10) = 24,750,000 L/ day

Next, calculate the average daily rate of usage per second, maximum average daily rate, and peak daily rate.

ADD = ADWD / 86,400 = 286.45 L/s

MDD = 1.44 * ADD = 412.5 L/s

PHD = 2.3 * ADD = 658 L/s