To split a shared cost in a house of rooms, pick a method (equally between rooms, by number of people or by room size), divide the cost, then round to the penny so the shares add up exactly to the bill. Below are worked examples with real numbers for a cleaner, broadband, running costs and a repair, plus what to do about odd pennies and part months.
This post is about the arithmetic. Whether you include a cost in the rent or ask tenants to pay a share depends on your tenancy agreements, and there are rules about what landlords can charge for, so check before you pass any cost on. Even if you never recharge a penny, knowing what each room costs you is how you set a sensible rent.
Three ways to split a cost
| Method | How it works | Good for |
|---|---|---|
| Equally | The cost divided by the number of rooms | Costs that don't depend on who's in the room, like cleaning shared areas |
| By number of people | The cost divided by the number of people, then multiplied by the people in each room | Costs that grow with each person |
| By room size | The cost divided by the total floor area, then multiplied by each room's size | Costs that grow with space, and pricing rooms |
Whichever you choose, write it down and use it every time. Tenants mind a change of method more than the method itself.
Example 1: a cleaner, split equally
A cleaner does the kitchen, bathrooms and hallway every fortnight, which comes to £120 a month. The house has 7 rooms, all let.
- £120 ÷ 7 = £17.142857…
- Rounded down to the penny, that's £17.14 a room.
- 7 × £17.14 = £119.98, so there are 2p left over.
- Two rooms pay £17.15, the other five pay £17.14.
Check: (2 × £17.15) + (5 × £17.14) = £34.30 + £85.70 = £120.
Rotate who pays the extra penny each month, or give it to the rooms with the largest leftover fraction. Either way, the shares always add up to the bill.
Example 2: broadband, split by number of people
Broadband costs £42 a month. There are 6 rooms: five with one person each and one with a couple, so 7 people in all.
- £42 ÷ 7 people = £6 a person.
- Each single room: 1 × £6 = £6.
- The couple's room: 2 × £6 = £12.
Check: (5 × £6) + £12 = £30 + £12 = £42.
Split equally between rooms instead, every room would pay £7. Splitting by people means the couple's room pays a bit more, and the single rooms a bit less.
Example 3: running costs, split by room size
Splitting by size is most useful for working out what each room costs you to run, before you set the rent. Say a house's shared running costs (insurance, broadband, the cleaner and a set-aside for repairs) come to £900 a month. It has five rooms:
| Room | Size | Share of floor area | Monthly share |
|---|---|---|---|
| Room 1 | 9 m² | 9 ÷ 60 | £135 |
| Room 2 | 11 m² | 11 ÷ 60 | £165 |
| Room 3 | 12 m² | 12 ÷ 60 | £180 |
| Room 4 | 14 m² | 14 ÷ 60 | £210 |
| Room 5 | 14 m² | 14 ÷ 60 | £210 |
| Total | 60 m² | £900 |
The quick way: £900 ÷ 60 m² = £15 per square metre, then multiply by each room's size. Room 1 is 9 × £15 = £135, Room 4 is 14 × £15 = £210.
Now you know Room 1 costs about £135 a month to run and Room 4 about £210. If both are let at the same rent, the larger room is earning you less, which is worth knowing when a room next comes free.
Measure each room once, from wall to wall, and keep the sizes with your records. Ignore cupboards and en-suites unless you include them for every room.
Example 4: a repair, spread over the year
The boiler needs a new part and a call-out: £1,140, in a house of 6 rooms.
- Per room: £1,140 ÷ 6 = £190.
- Spread over 12 months: £190 ÷ 12 = £15.833…, about £15.83 a room a month.
A one-off bill of £1,140 feels like a bad month. Seen as about £15.83 a room a month, it's a cost to plan for. Many landlords set aside a monthly amount per room for repairs for exactly this reason.
Some repairs belong to one room only. If the window in Room 3 needs a new handle for £85, that's Room 3's cost, not the house's. Record it against the room, so each room's real running cost stays accurate.
Example 5: a part month
Broadband is £42 for a 30-day period. Room 4 was empty for the first 12 days, so it was let for 18 days. The other five rooms were let for all 30 days.
- Room-days in total: (5 × 30) + 18 = 150 + 18 = 168.
- Cost per room-day: £42 ÷ 168 = £0.25.
- Each full room: 30 × £0.25 = £7.50.
- Room 4: 18 × £0.25 = £4.50.
Check: (5 × £7.50) + £4.50 = £37.50 + £4.50 = £42.
Part months rarely come out this neatly. When they don't, round each share to the penny and adjust one or two rooms by a penny so the total matches the bill.
Mistakes to avoid
- Shares that don't add up. Always check that the shares add up exactly to the bill. A penny out each month becomes an argument by the end of the year.
- Changing method half way through. If you must change, start from a new bill period and tell tenants first.
- Forgetting empty rooms. Decide in advance whether an empty room's share is your cost or spread across the others, and be consistent.
- Losing the working. Keep the bill, the dates and the calculation together. If a tenant asks how you got to £17.15, you can show them in a minute.
How Rentap helps
Each house in Rentap has a Shared bills page. Enter the bill, the supplier, its dates and the total, then choose how to split it: equally between rooms, by room size or by number of people. Rentap shares it between the rooms that had a tenancy during the bill's dates and makes sure the shares add up exactly to the total, giving the odd pennies to some rooms. It doesn't split by days, so for a part month like Example 5, work it out as above.
To split by room size, add each room's size in square metres on the room's page first. If you choose to, you can add each share to the tenant's account, where it appears on their balance and statement alongside their rent.
Repairs and other costs go in Expenses, against the house or the room, with a photo of the receipt. If you've agreed with a tenant that they'll repay a cost, you can add the amount to their account at the same time. The analytics page then shows income, expenses and net for each house, month by month.
For the rest of the month's jobs, see our monthly checklist for landlords who let rooms, or read how Rentap handles rent tracking room by room and repairs.
What it costs
1 month free, no card needed. Add a card during your trial and get 1 more month free. Then £2 a room a month. You pay for the number of rooms you choose. See the pricing page for the details.