Water Potential Calculator
Use our water potential calculator to calculate total water potential (Ψ) from solute potential (Ψs), pressure potential (Ψp), gravitational potential (Ψg), and hydrostatic potential (Ψh). Includes the water potential formula and what water potential measures in cells and plant biology.
What Does Water Potential Measure?
Water potential (Ψ) measures the potential energy of water compared to pure water under the same conditions. It helps predict the direction water will move, especially in plant cells, tissues, and soils.
Water moves from higher water potential to lower water potential. In biology classes, water potential is often used to explain osmosis, turgor pressure, and water movement into or out of cells.
Total water potential is commonly modeled as the sum of several components, including solute (osmotic) potential, pressure potential, and sometimes gravitational and hydrostatic terms depending on the system.
Water Potential Formula
This calculator adds the four water potential components to get total water potential (Ψ).
All terms should be in the same units (here, MPa).
A more negative Ψ indicates lower water potential.
How to Calculate Water Potential
- 1
Enter solute potential (Ψs) in MPa.
- 2
Enter pressure potential (Ψp) in MPa.
- 3
Enter gravitational potential (Ψg) in MPa.
- 4
Enter hydrostatic potential (Ψh) in MPa.
Frequently Asked Questions
A common model is Ψ = Ψs + Ψp + Ψg + Ψh, where total water potential is the sum of solute, pressure, gravitational, and hydrostatic potentials.
Water potential describes the tendency of water to move. Water moves from higher Ψ to lower Ψ, which helps explain osmosis and water movement in plants and cells.
In many cell-based problems, you calculate Ψ using Ψ = Ψs + Ψp and treat Ψg and Ψh as 0. Then compare Ψ inside and outside the cell to predict water movement.
It measures water’s potential energy relative to pure water, which lets you predict the direction of water movement in systems like cells, plant tissue, and soils.
In lab graphs (for example, percent mass change vs. solution concentration), you typically find the isotonic point first, then use that concentration to compute Ψs (often via an osmotic potential relationship) and combine it with Ψp as needed.