1. The house
A reception room you plan to let can be added as a room below.
Choose a region to see the default.
2. Let as one house
Choose a region and bedrooms to see the default.
Default 4% — the writer's assumption, about two weeks a year.
3. Let room by room
List each room you would let, with its floor area. If part of a room’s floor is under a ceiling lower than 1.5 m, enter that part in “Under 1.5 m ceiling” — it is not counted.
Room 1
Enter the floor area
m²m²£Room 2
Enter the floor area
m²m²£Room 3
Enter the floor area
m²m²£Room 4
Enter the floor area
m²m²£
Choose a region to see the room rent default. The minimum room sizes are licence conditions: see “What changes if you convert” below.
Default 8% — the writer's assumption.
4. Conversion and one-off costs
Default £11,500, the middle of £8,000–£15,000 per room for a mid-specification conversion — Renovat, “HMO Conversion Cost Manchester 2026” — trade estimate (27 Sep 2026). London is higher (Mayfair Studio, “HMO Conversion Cost London 2026” — trade estimate (20 Jul 2026)).
From a builder's quote. When entered, it replaces the per-room figure and the en-suite line.
Default £4,750, the middle of £3,500–£6,000 per en-suite — Renovat, “HMO Conversion Cost Manchester 2026” — trade estimate (27 Sep 2026).
Default £950, the middle of £700–£1,200 — Mayfair Studio, “HMO Conversion Cost London 2026” — trade estimate (20 Jul 2026).
Councils set their own fee. Check your council’s fee.
5. Running costs and finance
Your band's amount from your council. Counted as your cost when let room by room — see Council tax below.
Default £75 a month for each room to let — the writer's assumption.
Default £300 — the writer's assumption.
Of the rent collected. Defaults 5% and 8% — the writer’s assumptions.
An HMO mortgage can cost more. Leave both blank for figures before finance.
Your estimate
Estimates based on your inputs and the defaults shown above.
Choose a region and the bedrooms, and enter at least one room’s floor area, to see the estimate.
What changes if you convert
The rules in England, checked against the legislation in October 2026. Your council decides how they apply to your house.
Planning
Changing a house (use class C3) to a small HMO of not more than six residents (use class C4) is permitted development: the planning permission is granted by the General Permitted Development Order 2015 (Schedule 2, Part 3, Class L), so no application is made for the change of use itself.
A council can remove that right in an area with an Article 4 direction. Where one is in force, the change of use needs a planning application.
The fee for a planning application for a change of use is £610, from 1 April 2026. Fees change every 1 April.
More than six residents takes the house outside class C4. Whether planning permission is then needed depends on whether the change is a "material change of use" (Town and Country Planning Act 1990, s.55 and s.57), so ask your council.
Each council publishes its own Article 4 directions. Check your council’s planning pages before you buy or start work.
Read the guide: Article 4 directions and HMO planning permission
Licensing
An HMO licence is mandatory where five or more people, forming two or more households, live in an HMO (Housing Act 2004, s.55; SI 2018/221, art.4).
Your council may also run additional licensing, which covers other HMOs in an area, or selective licensing, which is not limited to HMOs. Check with your council: gov.uk has a postcode search for it.
Read the guide: HMO licensing in England: mandatory, additional and selective
Room sizes
Every HMO licence in England must include conditions on sleeping rooms: at least 6.51 m² for one person over 10, and at least 10.22 m² for two people over 10 (Housing Act 2004, Schedule 4, paragraph 1A).
Floor area where the ceiling is lower than 1.5 m is not counted.
A room under 4.64 m² may not be used for sleeping at all.
Council tax
Where a house is an HMO for council tax purposes, the owner pays the council tax, not the tenants (Local Government Finance Act 1992, s.8(3); Council Tax (Liability for Owners) Regulations 1992, Class C). This calculator counts it as your cost in the HMO column.
Tenancies and deposits
Where each room is let on its own tenancy, each deposit is protected separately, with its own prescribed information, within 30 days of receiving it (Housing Act 2004, s.213).
Read the guide: Letting an HMO room by room: deposits, rent, notice
Where the defaults come from
- ONS, Price Index of Private Rents — average monthly rent by region and bedrooms, September 2026 — 21 Oct 2026. Source: Office for National Statistics, licensed under the Open Government Licence v3.0.
- UK House Price Index (HM Land Registry, ONS) — average price by region, all property types, August 2026 (provisional) — 21 Oct 2026. Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
- SpareRoom Rental Index — average monthly room rent by region, Q3 2026, bills included — Oct 2026. © SpareRoom. Figures from SpareRoom’s published Rental Index, entered by hand and cited with attribution; not reproduced under an open licence.
- Renovat, “HMO Conversion Cost Manchester 2026” — trade estimate — 27 Sep 2026.
- Mayfair Studio, “HMO Conversion Cost London 2026” — trade estimate — 20 Jul 2026.
- Time empty, bills, insurance and maintenance defaults are the writer’s assumptions, not published figures.
- Trade estimates are what builders publish about their own work, not official statistics.
About these figures
Every figure here is an estimate based on your inputs and the defaults shown, which are averages and may not match your house, your street or your council. It is general information for England only, not financial, tax, mortgage or legal advice. Tax is not included. Get quotes, ask your council about planning and licensing, and take advice before you buy or build. Nothing you enter is sent or stored.