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Prorated Utility Bill Calculator

Enter the total bill, the days in the period, and the days you owe for.

How it is calculated

The tool gives each day of the billing period the same price. per day = total bill ÷ days in the period, then your share = per day × days you owe for, and remainder = total bill − your share, which is what is left for the other occupant or for the days you did not use. Enter the total bill in any currency (the tool writes a dollar sign, but it does no conversion), the number of days the bill covers, taken from the bill itself, and the number of days you are responsible for. The period must be more than zero and the days owed cannot be negative. If you enter more days than the period contains, the share exceeds the bill and the remainder turns negative. Amounts are rounded to two decimals. The method assumes flat use; it does not weigh heavy and light days.

Worked example

A gas bill of 142.50 covers a 30-day period, and you lived there for the last 11 days. Step 1: the daily price is 142.50 ÷ 30, which the tool shows as $4.75 per day. Step 2: your share is 4.75 × 11, so you owe $52.25. Step 3: the remainder is 142.50 − 52.25 = 90.25, the part for the other 19 days. The dollar sign is only a symbol; the numbers are in the currency of your bill.

Try this example →

Common mistakes

  • Using 30 days for every month. The period must be the number of days the bill actually covers, taken from the bill dates; a 31-day period of 186 gives 6.00 per day, not 6.20.
  • Counting the move-in or move-out day wrongly. Decide in advance whether both the first and the last day count, and use that same rule for both occupants, or the days will not add up to the period.
  • Entering the bill period as the days you owe. The second day field is the whole period, the third is only your days; swapping them gives the wrong share.
  • Prorating a bill that has a fixed charge and a usage charge as if both were the same. This tool spreads the total evenly per day, so a heavy-use month for one occupant is not reflected; use meter readings for that.
  • Expecting the remainder to stay positive. If the days owed exceed the period, the remainder becomes negative, which usually points to a typing error.

About this calculator

Prorating a bill means splitting its total cost in direct proportion to time used: daily rate = total bill ÷ total days in the billing period, and your share = daily rate × days you're responsible for. This treats the underlying usage as roughly even across the period, which is a reasonable assumption for a flat service charge even though actual consumption (like electricity use) may vary day to day.

Prorating comes up whenever occupancy doesn't line up cleanly with a utility company's fixed billing cycle — moving in or out mid-month, subletting for part of a period, or splitting a shared meter. Landlords, tenants, roommates, and property managers use this calculation to divide a water, gas, or electric bill fairly when only part of the billing period applies to a given occupant.

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Comments (1)

  • Editorial team

    This splits the bill evenly per day, which works for a move-in or move-out mid-cycle but hides the fact that heating or cooling use is rarely flat. If a tenant left during a cold month, a flat split may favour them. In that case compare it with the meter readings on the bill itself. Agree beforehand whether the move-in day counts. Did your last bill cover a period you could split by meter readings instead?

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