Everyday household math
This category covers two very different questions that both come up constantly around the house: how much water does something hold, and how much does something cost to run. Neither requires advanced math, but both are easy to get wrong by an order of magnitude if you mix up a unit somewhere — gallons and litres, watts and kilowatts.
Pool volume: shape matters more than you'd think
The Pool Water Volume Calculator handles both rectangular and round pools, and lets you enter either a single average depth or separate shallow-end and deep-end depths. That second option matters — a pool that slopes from 3 feet to 7 feet doesn't hold the same water as a pool that's a flat 5 feet throughout, even though the average is identical on paper. If your pool has any slope, use the split-depth input for a more accurate figure, since chemical dosing and fill-time estimates depend directly on getting the gallon count right.
Electricity cost: the standby-power trap
The Electricity Cost Calculator separates active usage hours from standby hours because a lot of household electronics draw a small but constant load even when they're "off." On a single day that's negligible. Averaged across a full year, standby draw on multiple devices can add up to a real line item on your bill — which is why the calculator lets you enter a standby wattage figure alongside your active-use hours instead of ignoring it.
Where these numbers come from
Both calculators need one number you'll have to supply from your own utility bill or equipment label: your electricity rate per kWh, and your pump or hose flow rate if you want a fill-time estimate. The calculators can't know these — they're specific to your provider and your equipment — so double-check them against your actual bill or spec sheet for an accurate result.
Frequently asked questions
How accurate is the pool volume estimate for an irregular shape?
The rectangular and round shape options assume a consistent cross-section. A freeform or kidney-shaped pool will only be approximated — for an irregular shape, break it into rectangular and round sections and add the results together for a closer estimate.
Where do I find my electricity rate?
Your utility bill lists a per-kWh rate, sometimes broken into tiers or time-of-use pricing. Use your average or peak rate depending on when the appliance typically runs.
Does standby power really matter for my electricity bill?
For a single device, usually not much. Across several always-plugged-in electronics over a full year, standby draw can add up to a noticeable portion of your bill — which is why it's a separate optional input rather than ignored.