Well Volume Calculator
Calculate well water volume in gallons and cubic feet. Enter diameter and depth for accurate volume estimates with charts. Free online well volume calculator.
About This Calculator
A well volume calculator is an essential tool for homeowners, farmers, hydrogeologists, and water management professionals who need to determine the total capacity of a cylindrical water well. Knowing your well's volume is critical for sizing water treatment equipment, calculating chlorination doses for well disinfection, estimating irrigation water availability, and planning pump placement.
The calculation is based on the standard geometric formula for a cylinder: V = π × r² × h, where r is the radius of the well (half the diameter) and h is the total depth. The result in cubic feet is then converted to US gallons using the conversion factor 7.48052 gallons per cubic foot. This assumes the well is a perfect cylinder — most drilled and dug wells are approximately cylindrical, making this formula accurate for practical purposes.
Well types vary widely around the world. In rural India, open dug wells with diameters of 4–12 ft and depths of 30–100 ft are common, providing water for drinking, cooking, and irrigation. In the United States, modern residential wells are typically drilled with 4–8 inch casings and range from 100–300 ft deep. The United Kingdom has a mix of historic shallow wells (50–150 ft) and modern boreholes. This calculator adapts to all sizes — simply enter your well's diameter and depth in feet.
It is important to note that the calculated volume represents the total cylindrical bore volume, not the actual water storage. The water volume within a well depends on the water table depth and the aquifer's recharge rate. During dry seasons, the water level may drop significantly, reducing available water. For accurate water budgeting, measure the depth to water (static water level) and subtract it from the total depth before calculating water volume.
The interactive Volume by Depth chart shows how the total capacity increases as depth increases, giving you a visual understanding of your well's profile. The Well Dimensions chart compares diameter and depth for a quick dimensional reference. Use the share button to save and share your results with contractors, well drillers, or water treatment professionals.
Well Volume Calculator FAQ
How do you calculate well volume?
Well volume is calculated using the formula for the volume of a cylinder: V = π × r² × h, where r is the radius (half the diameter) and h is the depth. The result in cubic feet is multiplied by 7.48052 to convert to US gallons. For example, a 4 ft diameter well that is 100 ft deep holds approximately 9,400 gallons.
What units does the well volume calculator use?
This calculator uses feet for diameter and depth measurements. Results are displayed in both US gallons and cubic feet. One cubic foot equals approximately 7.48 US gallons. If you need metric results, convert your measurements: 1 foot = 0.3048 meters, and 1 cubic meter = 264.17 gallons.
What is the typical diameter of a residential well?
Residential water well diameters vary by region and well type. Dug wells (common in rural areas) are typically 3 to 10 feet in diameter. Drilled wells with casing are much narrower — usually 4 to 8 inches (0.33 to 0.67 ft). In India, open dug wells commonly range from 4 to 12 ft in diameter, while tube wells are 4 to 8 inches.
What is the average depth of a water well?
Well depths vary significantly by location and water table depth. In the US, residential wells average 100 to 300 ft deep. In India, dug wells are typically 30 to 100 ft deep, while borewells can reach 200 to 500 ft. In the UK, wells average 50 to 200 ft. Always consult local hydrogeological data when planning a well.
Is the calculated well volume the same as available water volume?
No, the calculated volume represents the total cylindrical volume of the well bore, not the amount of water available. The actual water volume depends on the water table level, recharge rate of the aquifer, and well construction. A well may only be partially filled with water. The useful water volume is the volume between the static water level and the pump intake.
How much water does a typical well hold?
A standard 4-ft diameter, 100-ft deep well holds about 9,400 gallons of total cylindrical volume. A narrower 6-inch diameter, 200-ft deep drilled well holds about 293 gallons. The actual usable water depends on the water level. A dug well with 20 ft of water depth and 4 ft diameter contains about 1,880 gallons of water.
Why is it important to know your well volume?
Knowing your well volume helps in several ways: sizing water treatment systems (softeners, filters), calculating disinfectant dosing (chlorination shock treatment), estimating available water for irrigation or livestock, planning pump capacity and placement, and understanding well yield during dry seasons. It is a fundamental parameter for well management.
How often should a well be measured?
Well volume should be measured when the well is first constructed, after any deepening or rehabilitation work, and periodically (every 1-2 years) to track sediment buildup or changes in the water column. A reduction in volume over time may indicate siltation, biofilm accumulation, or mechanical damage to the well casing.