Water Bill Calculator Formula
Understand the math behind the water bill calculator. Each variable explained with a worked example.
Formulas Used
Usage Charge
usage_charge = monthly_gallons / 1000 * rate_per_1000_galTotal Monthly Bill
total_bill = base_fee + monthly_gallons / 1000 * rate_per_1000_galMonthly Gallons Used
gallons_used = monthly_gallonsVariables
| Variable | Description | Default |
|---|---|---|
gallons_per_day | Daily Water Usage(gal) | 80 |
rate_per_1000_gal | Rate Per 1,000 Gallons(USD) | 6.5 |
base_fee | Monthly Base Fee(USD) | 15 |
days_in_month | Days in Month | 30 |
monthly_gallons | Derived value= gallons_per_day * days_in_month | calculated |
How It Works
How Water Bills Are Calculated
Most water utilities charge a flat base fee plus a per-unit usage charge.
Formula
Monthly Bill = Base Fee + (Daily Usage x Days / 1,000) x Rate Per 1,000 Gallons
Worked Example
80 gallons/day, $6.50 per 1,000 gallons, $15 base fee, 30-day month.
gallons_per_day = 80rate_per_1000_gal = 6.5base_fee = 15days_in_month = 30
- 01Monthly usage = 80 x 30 = 2,400 gallons
- 02Usage charge = 2,400 / 1,000 x $6.50 = $15.60
- 03Total bill = $15.00 + $15.60 = $30.60
Ready to run the numbers?
Open Water Bill Calculator