Soil Moisture Percentage Calculator
Calculate gravimetric and volumetric soil water content from wet/dry weight and bulk density measurements.
Results
What is it?
Soil moisture content is measured gravimetrically by comparing the wet and oven-dry weight of a sample. Gravimetric water content (g water / g dry soil) × 100%. Volumetric water content (m³ water / m³ soil) = gravimetric × bulk density. Volumetric content is needed for irrigation scheduling because it relates to the volume of water available per unit of soil volume.
How to use
Collect a soil sample, weigh it before drying (wet weight), dry at 105°C for 24 hours in an oven, then weigh again (dry weight). Enter both weights and the approximate bulk density for your soil type. The calculator returns both moisture metrics and the water volume held per cubic metre of soil.
Example scenario
Wet weight 150 g, dry weight 120 g: gravimetric = (150−120)/120 × 100 = 25%. For loam soil (BD = 1.3 g/cm³): volumetric = 25 × 1.3 = 32.5%. This is within the typical field capacity range (30–40%). Water held = 325 liters/m³ of soil.
Pro tip
Field capacity (FC) is typically 30–40% volumetric, permanent wilting point (PWP) 10–15%. The plant-available water = FC − PWP. Irrigate when soil reaches 50% depletion of available water for most crops, or 35% for stress-sensitive crops like vegetables. Microwave drying (2–3 min at medium power) can approximate oven-dry weights in the field as a rapid check method.