Owning a pool is a great way to relax, exercise, and enjoy quality time with family and friends. But whether you’re filling your pool for the first time, planning chemical treatments, or estimating water costs, one essential detail you need to know is your pool’s size and capacity.
That’s where our Pool Size Calculator comes in. With just a few quick inputs—your pool’s length, width, and average depth—this tool instantly gives you the pool’s volume in cubic feet and capacity in gallons. This saves you time, ensures accurate water treatment, and helps you budget for pool maintenance.
In this article, we’ll show you how to use the calculator step by step, explore practical use cases, and answer the most common questions about pool sizing and water capacity.
Pool Size Calculator
How to Use the Pool Size Calculator (Step by Step)
Using the calculator is quick and simple. Follow these steps:
- Enter the Length (ft):
Type in the length of your pool in feet. For irregularly shaped pools, use the longest straight length. - Enter the Width (ft):
Input the pool’s width in feet. Again, if your pool has curves or irregular sides, measure the widest point for the most accurate estimate. - Enter the Average Depth (ft):
Measure the shallowest and deepest parts of your pool. Add them together and divide by two to get the average depth. Enter this value. - Click “Calculate”:
The tool will instantly display:- Pool Volume in cubic feet
- Pool Capacity in gallons
- View Results:
Your pool’s measurements will appear in a results box. You can use the “Reset” button to start again.
Practical Example
Let’s say you have a rectangular backyard pool with the following dimensions:
- Length: 30 ft
- Width: 15 ft
- Average Depth: 5 ft
Step 1: Multiply length × width × depth
30 × 15 × 5 = 2,250 cubic feet
Step 2: Convert cubic feet to gallons (1 cubic foot = 7.48 gallons)
2,250 × 7.48 = 16,830 gallons
So, your pool holds approximately 16,830 gallons of water.
This information is extremely useful for:
- Knowing how much water you’ll need to fill the pool.
- Determining how much chlorine or pool shock to add.
- Estimating your water bill when refilling.
Why Knowing Your Pool’s Capacity is Important
Accurately calculating your pool’s size and capacity is more than just a number—it impacts pool care, safety, and costs. Here’s why it matters:
- Chemical Balance: Adding too much or too little chlorine, algaecide, or pH adjuster can make your pool unsafe or ineffective. Correct volume ensures precise chemical treatment.
- Heating Efficiency: Pool heaters depend on water volume to calculate how long it will take to warm the pool.
- Water Conservation: Knowing capacity helps you estimate refilling needs and avoid water waste.
- Maintenance Planning: Helps pool professionals provide accurate service quotes.
- Budgeting: Water and chemical costs depend on pool size.
Extra Helpful Tips for Pool Owners
- Irregular Shapes: For oval, kidney, or round pools, measure the longest points and average depth for a close estimate.
- Average Depth Calculation: If shallow end is 3 ft and deep end is 7 ft → (3 + 7) ÷ 2 = 5 ft average depth.
- Seasonal Use: Draining and refilling? Knowing gallons helps estimate both cost and time.
- Safety First: Always double-check pool volume before adding chemicals to avoid health risks.
Frequently Asked Questions (FAQs)
Here are the most common questions pool owners ask about pool size and capacity:
1. How do I calculate pool volume for an oval or round pool?
For oval pools, multiply length × width × average depth × 0.89. For circular pools, multiply diameter × diameter × depth × 5.9.
2. What is the formula used by the Pool Size Calculator?
The calculator multiplies length × width × average depth to get cubic feet, then converts it to gallons using 1 cubic ft = 7.48 gallons.
3. Why is average depth important?
Most pools have shallow and deep ends. Average depth ensures you get an accurate water capacity instead of overestimating or underestimating.
4. How many gallons are in a typical backyard pool?
Most residential pools hold between 10,000 and 30,000 gallons depending on size and shape.
5. Can I use this calculator for above-ground pools?
Yes, as long as you know the measurements, the calculator works for both above-ground and inground pools.
6. Do I need exact measurements?
The closer your measurements are, the more accurate the result. Small measurement errors won’t significantly affect chemical treatment.
7. How do I know how much chlorine to add?
Pool chemicals are dosed based on gallons. Once you know capacity, check the label for correct dosage per 10,000 gallons.
8. How do I calculate water cost for filling my pool?
Multiply total gallons by your local water rate per gallon (or per 1,000 gallons). This gives you an estimated fill cost.
9. Can this tool help with hot tubs or spas?
Yes. Enter smaller dimensions and it will calculate volume and capacity for spas as well.
10. How accurate is the conversion factor (7.48 gallons per cubic ft)?
It’s exact: 1 cubic foot of water equals 7.48 U.S. gallons.
11. What if my pool has sloped floors?
Measure shallow and deep ends, then use the average depth. This provides the closest estimate.
12. Why is my pool water bill higher than expected?
Evaporation, leaks, and splash-out can increase water usage beyond the initial fill volume.
13. Can I use rainwater to refill my pool?
Yes, but you’ll still need to balance chemicals properly since rainwater can alter pH levels.
14. How often should I measure my pool?
Only once, unless you remodel or change dimensions. Volume doesn’t change unless the structure does.
15. Is there a difference between U.S. gallons and Imperial gallons?
Yes. This calculator uses U.S. gallons. One Imperial gallon equals 1.2 U.S. gallons.
16. Can I use this for saltwater pools?
Yes, knowing gallons is essential for calculating the correct amount of salt to add.
17. What if my pool has multiple depths and shapes?
Divide the pool into sections, calculate each section’s volume, then add them together.
18. Does pool size affect filtration system requirements?
Absolutely. Pool filters and pumps are sized based on total gallons to ensure proper circulation and cleaning.
19. How much does water weigh in my pool?
One gallon of water weighs about 8.34 pounds. Multiply your pool’s gallons by 8.34 to find total water weight.
20. Can I use the calculator for metric units?
Currently, this version uses feet and gallons. You can convert meters to feet before entering values.
Final Thoughts
Knowing your pool’s volume and capacity is essential for safe, efficient, and cost-effective pool ownership. Our Pool Size Calculator takes the guesswork out of pool measurements, giving you instant results in both cubic feet and gallons.