How much water is in my well? Find your well water volume in gallons and litres, compute well casing volume per foot, size a 3x well purge volume for sampling, dose shock chlorination bleach in fluid ounces, and measure well recovery rate — imperial and metric.
Answer: how much water in my well right now. Enter casing diameter, total depth, and static water level.
| Measure | Value |
|---|---|
| Water volume | 556.00 L |
| Water volume | 0.5560 m3 |
| Gallons per foot of casing | 1.4688 gal/ft |
| Full casing volume (to bottom) | 293.76 gal |
Volume = pi times radius squared times water-column height; 1 US gallon = 231 cubic inches.
For square or rectangular dug wells. Enter inside dimensions.
| Measure | Value |
|---|---|
| Volume | 320.00 ft3 |
| Volume | 9,061.39 L |
Volume = length times width times depth; 1 cubic foot = 7.48052 gallons.
Purge stagnant casing water before sampling so the sample represents the aquifer.
| Measure | Value |
|---|---|
| Purge volume | 1,668.00 L |
EPA monitoring-well sampling guidance: purge at least 3 well volumes before collecting a sample.
How much bleach to shock a well: pick a target chlorine level and your bleach strength. Use plain unscented household bleach.
| Measure | Value |
|---|---|
| Cups | 2.24 cups |
| Pints | 1.12 pints |
| Quarts | 0.56 quarts |
| Millilitres | 529.5 mL |
Dose formula: fluid ounces = gallons times 128 times ppm divided by (bleach percent times 10,000). Spot-checked against the Rhode Island Department of Health Well Disinfection Procedure (September 2026). This shock chlorination calculator doubles as a well disinfection bleach calculator for any bleach strength. Let chlorine sit 6 to 12 hours, then flush until no chlorine smell remains. Do not drink until flushing is complete.
Time how long it takes to pump a known volume.
| Measure | Value |
|---|---|
| Time to recover full well volume | 20.0 min |
Recovery rate = gallons pumped divided by minutes. This well recovery rate calculator also estimates refill time. Compare with your pump rating before sizing equipment.
Well water volume gallons per foot of water column, by inside casing diameter — this gallons per foot well casing chart is computed as pi times radius squared times 12 inches, divided by 231 cubic inches per gallon.
| Casing diameter (in) | Gallons per foot |
|---|---|
| 2 | 0.1632 |
| 4 | 0.6528 |
| 6 | 1.4688 |
| 8 | 2.6112 |
| 10 | 4.0800 |
| 12 | 5.8752 |
| 16 | 10.4448 |
| 20 | 16.3200 |
| 24 | 23.5007 |
| 36 | 52.8767 |
Multiply your water column height by the gallons per foot of your casing. A 6-inch casing holds 1.4688 gallons per foot, so 100 feet of water in a 6-inch well is 146.88 gallons (about 556 litres). Measure from the static water level down to the bottom of the well, not the total drilled depth.
Use the cylinder formula: volume equals pi times radius squared times water-column height. In well terms: gallons equals gallons-per-foot of your casing diameter times feet of water. A 6-inch well at 1.4688 gallons per foot with 100 feet of water holds 146.88 gallons.
A 6-inch casing holds 1.4688 gallons per foot (about 1.47) -- the 6 inch well gallons per foot figure most owners look up. Other common sizes: 4-inch 0.6528, 8-inch 2.6112, 10-inch 4.0800, 12-inch 5.8752, 24-inch 23.5007 gallons per foot. The full reference table is in the gallons-per-foot tab above.
Purge volume is the water you pump out before collecting a sample, so the sample represents fresh aquifer water instead of stagnant casing water. EPA monitoring-well sampling guidance calls for at least 3 well volumes. For a 146.88-gallon well, that means purging 440.64 gallons before sampling.
It depends on your water volume, target chlorine level, and bleach strength. Example: 146.88 gallons of well water dosed to 50 ppm with 5.25 percent household bleach needs 17.91 fluid ounces (2.24 cups). Dosing the same well to 200 ppm needs 71.62 fluid ounces (4.48 pints). The shock chlorination calculator tab above does this math for any well.
Most state and university guidance says 6 to 12 hours: add the bleach in the evening, let it sit overnight, and flush in the morning. Run each faucet until you smell chlorine so the whole plumbing system is disinfected, then flush to waste away from the well and septic system until the chlorine smell is gone.
Dug wells are usually square or rectangular: volume equals length times width times depth, times 7.48052 gallons per cubic foot. A 4 by 4 foot well with 20 feet of water holds 320 cubic feet, which is 2,393.77 gallons.
Pump a known volume and time it: recovery rate in gallons per minute equals gallons pumped divided by minutes. If you purge 440.64 gallons in 60 minutes, the well recovers at about 7.34 gallons per minute. Low-yield wells recover slowly, so retest after heavy use before sizing a pump.
Yes. Switch the unit toggle to metric. Example: a 150 mm casing with 30 metres of water holds 0.5301 cubic metres, which is 530.14 litres (140.05 gallons).
No. Do not drink the water until you have flushed the system completely and can no longer smell chlorine. Chlorination disinfects against bacteria but does not remove chemical contamination. Follow EPA and your state health department guidance, and test your well water at least once a year.
The dose formula is: fluid ounces equals water gallons times 128 times target ppm, divided by bleach percent times 10,000. Every value was spot-checked against the Rhode Island Department of Health Well Disinfection Procedure (September 2026). Example: 100 feet of water in a 6-inch casing at 50 ppm with 5.25 percent bleach needs 17.91 fluid ounces, matching their published table value of 18 ounces.