How to split a rent increase between roommates

How much more does each roommate pay after a rent increase?

Start with the size of the raise. Say three roommates share a $2,700 apartment, with rooms priced at $1,100, $900 and $700, and the rent goes up 5% to $2,835. The raise is $2,700 times 0.05, which is $135 a month. The only open question is who pays which part of the $135.

Which three ways can you share a rent increase?

You can add the same dollars to every room, add the same percentage to every room, or re-run the rule that set the original rent.

1. Equal dollars. Divide the raise by the number of people. $135 divided by 3 is $45 each. The dollar gap between the rooms stays exactly as it was.
2. The same percentage on each room. Every room rises 5%. The $1,100 room adds $55, the $900 room adds $45 and the $700 room adds $35. The percentage gap stays the same, and the bigger room carries more of the raise.
3. Re-run the original rule. Apply whatever method set the rent in the first place to the new total. The next section shows what that gives.

Both of the first two collect the same $2,835. Only the biggest and smallest rooms move, by $10 a month each way.

Room	Now	Equal dollars	Same 5%
Room A	$1,100	$1,145	$1,155
Room B	$900	$945	$945
Room C	$700	$745	$735
Total	$2,700	$2,835	$2,835

Over a 12-month lease, that $10 a month is $120 a year. The raise costs room A $660 under the percentage rule and $540 under equal dollars, and it costs room C $420 or $540.

What does re-running the original rule give you?

It lands on one of the first two answers, depending on how the rent was set in the first place.

• Weights. If the rooms were priced by square feet, income or feature points, the weights stay and the total grows. Take weights of 11, 9 and 7, which add to 27 and produce the $1,100, $900 and $700 rooms. $2,835 divided by 27 is $105 a share, so the rooms become $1,155, $945 and $735. That is the same answer as the percentage rule, because every room keeps its share of the total. How to split rent by room size and how to split rent based on income show where weights like these come from.
• A base plus premiums. If the rent is an equal $900 base with the $1,100 room paying $200 over and the $700 room paying $200 under, the premiums are fixed in dollars. The raise goes onto the base, which gives $45 each and matches equal dollars.

Choosing between the rules is a question of what the original deal was. How to split rent fairly covers how to set that deal in the first place.

Does a bigger raise change the answer?

The gap between the rules grows with the size of the raise. Say the rent goes from $2,700 to $3,000, which is $300 more a month or 11.1%.

• Equal dollars: $100 each, so the rooms become $1,200, $1,000 and $800.
• Weights of 11, 9 and 7: $122.22, $100.00 and $77.78, so the rooms become $1,222.22, $1,000.00 and $777.78.

Room A now pays $22.22 a month more under weights than under equal dollars, against $10 at the $135 raise. The bigger the raise, the more the choice matters, so decide the method before you know the number.

What if the raise starts mid-month?

Prorate the first month. Say the new rent starts on the 16th of a 30-day month. Days 1 to 15 carry the old rent and days 16 to 30 carry the new one, which is 15 days each.

The raise for that month is $135 times 15 divided by 30, or $67.50, which is $4.50 a day. Split equally, that is $22.50 each. By the same percentage it is $27.50, $22.50 and $17.50. From the next month, the full amounts apply.

The prorated rent calculator does the day count, and what prorated rent means explains the term. Check what the landlord actually bills for that month first, and split that figure.

What should the roommate agreement say?

Write the rule down once so a future raise needs no new argument. Four lines are enough:

• The method: equal dollars, the same percentage, or re-running the original rule.
• The start: the date the new split applies and how the first partial month is prorated.
• The notice: how soon after hearing about a raise each person tells the others.
• The rounding: who takes any leftover cent, or that shares are rounded to the cent.

What to include in a roommate agreement lists the other topics, and the roommate agreement template has blanks for each one.

How do you record the new rent in EvenOut?

EvenOut can repeat rent for you, so a raise means replacing the repeating expense. Open the group’s “…” menu, choose “Repeating expenses”, pick the rent and tap “Stop repeating”; expenses already added stay. Then add the new rent with “Paid by” set to whoever pays the landlord, choose “Exact amounts” and type each person’s new figure from the table (or “By shares” with 11, 9 and 7 for the same-percentage result), and set Repeat to Monthly. Splits are cent-accurate, so a share like $1,222.22 works without rounding by hand.

Once the group agrees on a method, how to split rent fairly is the guide to keep for the next raise.