Enter the field capacity and the wilting point into the Calculator. The calculator will evaluate the Plant Available Water. 

Plant Available Water Formula



  • PAW is the Plant Available Water ()
  • FC is the field capacity
  • WP is the wilting point

To calculate plant available water, subtract the wilting point from the field capacity.

How to Calculate Plant Available Water?

The following steps outline how to calculate the Plant’s Available Water.

  1. First, determine the field capacity. 
  2. Next, determine the wilting point. 
  3. Next, gather the formula from above = PAW = FC – WP.
  4. Finally, calculate the Plant’s Available Water.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

field capacity = 95

wilting point = 60


What is field capacity in the context of plant soil?

Field capacity refers to the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. This is the point at which the soil holds the maximum amount of water it can without being saturated, and it provides an optimal condition for plant growth.

How does the wilting point affect plant growth?

The wilting point is the minimal point of soil moisture the plant requires not to wilt. If the soil moisture drops below this point, plants begin to wilt and can no longer recover their turgidity even if watered. It critically affects plant growth as prolonged exposure to conditions below the wilting point can lead to plant death.

Why is calculating Plant Available Water (PAW) important?

Calculating Plant Available Water is crucial for efficient water management in agriculture and horticulture. It helps in determining the exact amount of water that is available to plants for uptake. This can aid in optimizing irrigation practices, conserving water, and ensuring the health and productivity of crops.

Can the Plant Available Water vary between different soil types?

Yes, the Plant Available Water can significantly vary between different soil types due to variations in soil texture, structure, and organic matter content. Sandy soils, for example, have lower field capacity and hence lower PAW compared to clayey soils, which can hold more water at field capacity.