Water Volume Calculator
Use this water volume calculator to estimate gallons, liters, cubic feet, cubic meters, water weight, fill time and estimated cost for tanks, pools, pipes, ponds, aquariums and containers.
This tool is built for real jobs: filling a pool, sizing a tank, checking aquarium volume, estimating water in a pipe, calculating pond water, planning water delivery, or understanding a large water bill.
Quick answer: how do you calculate water volume?
For a rectangular tank, multiply length × width × water depth. If the measurement is in feet, the result is cubic feet. Multiply cubic feet by 7.48052 to get US gallons.
For a round tank, cylinder or pipe, use radius × radius × π × length or height. This calculator does the conversion automatically and gives practical outputs in gallons, liters, water weight, fill time and cost.
Water Volume Calculator
Choose the shape, enter dimensions, and select the unit. Add optional flow rate and water cost to estimate fill time and cost.
For rectangular tanks, enter length, width and water depth.
Water volume formulas used
| Shape | Formula | Best for |
|---|---|---|
| Rectangular tank | Length × width × depth | Aquariums, rectangular pools, storage tanks, troughs and containers. |
| Round tank / cylinder | π × radius² × height | Cylindrical tanks, barrels, vertical tanks and round containers. |
| Pipe / hose | π × radius² × pipe length | Estimating water held inside pipes, hoses and irrigation lines. |
| Pond estimate | Length × width × average depth × 0.85 | Irregular ponds or pools where corners and curves reduce full rectangle volume. |
| Custom volume | Entered cubic volume converted to gallons and liters | When you already know cubic feet, cubic meters or another cubic measurement. |
Useful examples
A 48 in × 18 in × 20 in aquarium holds about 75 gallons before subtracting gravel, rocks and decorations.
A 20 ft × 12 ft pool with 4 ft average depth holds about 7,181 gallons.
A 6 ft diameter round tank with 5 ft water height holds about 1,058 gallons.
A pipe holds less water than many people expect, but long irrigation or service lines can add up quickly.
Use gallons or liters to estimate how many truck loads, tank fills or storage containers are needed.
Pool filling, pond filling or tank filling can create a large bill. Use the cost estimate before filling.
Common mistakes that give wrong water volume
| Mistake | Why it matters | Fix |
|---|---|---|
| Using outside tank dimensions | Wall thickness can reduce actual inside volume. | Measure inside length, width and water depth when possible. |
| Using full height instead of water depth | A tank is often not filled to the top. | Use actual water depth, not total container height. |
| Forgetting average pool depth | Sloped pools have shallow and deep ends. | Use average depth: shallow depth + deep depth ÷ 2. |
| Ignoring rocks, gravel or equipment | Aquarium decorations and pond features displace water. | Treat the result as maximum volume and subtract displacement if needed. |
| Using gallons for billing only | Water bills may include sewer, stormwater, base charges and taxes. | Use this calculator for usage, then check your utility’s rate structure. |
When to contact your water department
Use this calculator for volume. Contact your local water department or utility when the fill may affect billing, sewer charges, leak adjustment, hydrant meter use or water restrictions.
Water Volume Calculator FAQs
How do I calculate water volume in gallons?
Calculate cubic feet first, then multiply by 7.48052. For a rectangular tank, cubic feet equals length × width × water depth in feet.
How many gallons are in a cubic foot of water?
One cubic foot of water equals about 7.48052 US gallons.
How many liters are in one gallon?
One US gallon equals about 3.78541 liters.
How much does water weigh?
One US gallon of water weighs about 8.34 pounds. One liter of water weighs about 1 kilogram.
How do I calculate pool water volume?
For a rectangular pool, multiply length × width × average depth in feet, then multiply by 7.48052 to get gallons.
How do I calculate round tank volume?
Use π × radius² × height. Radius is half of the diameter.
How do I calculate pipe water volume?
Use π × radius² × pipe length. Make sure diameter and length use the same unit before converting.
Can this estimate my water bill?
It can estimate water usage cost if you enter a cost per 1,000 gallons. Your actual bill may also include sewer, fixed charges, stormwater, taxes and previous balance.
Last editorial check: June 2026. Conversion constants are standard approximations. Actual container volume may vary by shape, wall thickness, slope, fittings and displacement.
Pay Smarter, Check High Bills, Start Service, Avoid Shutoff and Find Official Water Department Links
Use this free tool before paying a water bill, setting up autopay, starting or stopping service, checking a high bill, requesting leak help, or looking for the official water department portal. It gives practical next steps without collecting your account number or personal details.
What water bill or service problem do you need to solve?
Choose your situation. The tool will suggest the safest next step, what to prepare, and which official page to check first.
Start from the official water department, city, county or utility website before entering account details. Avoid random payment ads and look-alike bill pay sites.
Before paying a very unusual bill, check meter reads, toilet leaks, irrigation use, estimated bills, late fees, and whether your utility offers a leak adjustment.
Water Bill Payment Route Helper
Choose how you want to pay. The tool will tell you what to prepare and the safest payment path.
High Water Bill Checker
Compare your normal bill with the new bill and get a practical investigation path before calling customer service.
Leak Check and Adjustment Checklist
Use this before requesting a leak adjustment, disputing a bill, or calling the water department about high usage.
Start, Stop or Transfer Water Service Helper
Use this before moving, opening a new account, closing an old account, or transferring service to another address.
Past Due, Shutoff and Reconnection Helper
Use this if your account is late, disconnected, at risk of shutoff, or you need a payment plan or assistance program.
Simple Water Usage Cost Estimator
Estimate a rough bill from base charge, usage units, rate per unit, sewer charge, stormwater fee and service fees. Official tiered rates may be different.
Official Water Department Resource Finder
Enter city/utility and state to create safe searches for the official water bill portal, phone number, outage page, assistance, start service, leak adjustment, and Water-Department.org guide.
Water Department vs Payment Processor
- Water department: account help, service start/stop, leaks, repairs, shutoff, assistance.
- Payment processor: card/eCheck payment screen, payment fee, confirmation number, posting time.
Best sitewide placement
Add this tool after the main payment section or before FAQs. It helps users solve the next problem after reading the article.
Important safety note
This tool gives educational guidance only. Always confirm payment portals, phone numbers, account balance, assistance rules and reconnection steps with the official water department or utility.