Utility Bill Split Calculator
Divide a shared utility bill among people by proportional weight, square footage, or any other share you choose.
Equal share (per person)
$90
Weighted share (per row)
What is a proportional bill split?
A proportional split divides a shared bill by assigned weights rather than equally among everyone. The classic equal split – total divided by headcount – works when each person’s share of the underlying cost is the same. A proportional split handles the common case where it is not: roommates with different-sized bedrooms, tenants who share a commercial space in different ratios, or housemates who agreed on an unequal arrangement.
The weight can be any positive number: 1 for equal shares, room square footage for area-based splits, or days of occupancy for time-based splits. The calculator normalizes the weights so only their ratios matter, not their absolute size.
Equal-share amount is shown alongside the weighted breakdown so you can see both approaches at once.
How to calculate a weighted bill split
Formula
each person's share = total bill x (person's weight / sum of all weights)
How the formula works
Each person’s share = total bill x (person’s weight / sum of all weights). The sum of all weights is the denominator; each person’s weight over that sum gives their fraction of the bill. Multiplying by the total bill gives their dollar amount, rounded to the nearest cent.
The equal share is simply the total divided by the number of people, also rounded to the nearest cent.
Choosing weights
Any consistent unit works as long as everyone uses the same basis:
- Square footage of each person’s private space (bedrooms + proportional common area)
- Days occupied in the billing period
- A ratio agreed in writing (for example, 2:1 where one person takes the primary bedroom)
- 1 for each person to produce an equal split
Rounding
Per-person shares are rounded to the nearest cent. With three or more people, the rounded shares may sum to one cent more or less than the total. The convention in most shared-housing situations is to assign the extra cent to the person with the largest share. Agree on this before finalizing the split.
Checking the result
The sum of all weighted shares should equal the total bill within one cent. If your sum is off by more, check that you entered the correct total and that the weights reflect the agreed arrangement.
Example
- 1Sum of weights30 + 15 = 45
- 2Person 1 share$180 x (30 / 45) = $120
- 3Person 2 share$180 x (15 / 45) = $60
- 4Check: shares sum to total$120 + $60 = $180
FAQ
What can I use as a weight?
Anything proportional to the person's share of the bill. Common choices: 1 for each person (equal split), square footage of each bedroom or unit, days occupied in the billing period, or an agreed ratio. The calculator normalizes the weights, so their absolute values do not matter -- only their ratios.
How do I split equally?
Enter weight 1 for every person. The equal-share result at the top always shows the exact equal split regardless of weights.
Do the weighted shares add up to exactly the total bill?
They should within rounding. Each per-person share is rounded to the nearest cent. With many people, rounding can produce a sum that differs by one cent from the total. Assign the extra cent to one person before paying -- the typical convention is to give it to the person with the largest share.
Is this a legally binding split?
No. This calculator produces estimates for informational purposes only. Users should verify the result and consult any relevant lease, roommate agreement, or utility contract before splitting bills.
Sources
1. Tenant Rights and Utilities
Massachusetts Attorney General's Office
Provides context on how utilities are handled in shared housing and tenant obligations; referenced for informational framing of shared-bill calculations.
https://www.mass.gov/info-details/tenant-rights-and-utilities