A House in Multiple Occupation (HMO) is let room-by-room to three or more unrelated tenants who share facilities such as a kitchen or bathroom, rather than to a single household on one tenancy. Because each room earns its own rent, HMOs typically generate a higher total rental income than letting the same property as a single, whole-house tenancy — but that higher income comes with extra costs and regulation: mandatory licensing in many cases, stricter fire safety rules, a heavier management burden, and often bills included in the rent. This calculator works out your gross and net HMO yield after those costs, and shows you the uplift versus a standard single-let on the same property.
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You are letting this property room-by-room as a House in Multiple Occupation. Gross rent is calculated across all lettable rooms, then a void allowance, bills (if included), licensing, management and maintenance costs are deducted to arrive at a net annual income and net yield.
Gross annual rent = rooms × average monthly rent per room × 12. Net annual income deducts the void allowance, utility bills (if included in rent), the annual HMO licence cost, the management/letting fee, and maintenance/insurance. Both gross and net yield are expressed as a percentage of the property purchase price.
Your calculation summary shows a gross annual HMO rent of £0, a net annual income of £0 after all deductions, and a net HMO yield of 0.00% on a purchase price of £0.
This calculator is provided for general guidance only and uses a simplified, single average room rent and flat annual cost assumptions. Actual HMO performance depends on your specific property, local demand, council licensing conditions and running costs — always verify figures with a letting agent experienced in HMOs, your local authority, and an accountant before committing to a purchase.
A House in Multiple Occupation (HMO) is, under the legal definition set out in the Housing Act 2004, a property occupied by three or more tenants who are not members of a single household (not, for example, all one family) and who share basic amenities like a kitchen, bathroom or toilet. Each tenant typically has their own tenancy agreement for their room, rather than everyone being named on one joint tenancy for the whole property, which is the arrangement used for a standard single-let.
Common examples include shared student houses, house-shares for young professionals, and purpose-converted bedsit-style buildings. The defining features are the number of unrelated occupants and the sharing of facilities — a couple and their children renting a whole house together on one tenancy is not an HMO, no matter how many bedrooms it has.
Since 1 October 2018, mandatory HMO licensing applies nationally to any property let to 5 or more people forming 2 or more separate households who share amenities — this is now the case regardless of how many storeys the building has. Before that date, mandatory licensing only applied where the building also had three or more storeys; that storey requirement was removed, bringing single-storey and two-storey five-plus-occupant HMOs into scope as well.
On top of the national mandatory scheme, many local councils run their own additional licensing (covering smaller HMOs in their area) or selective licensing (covering all private rentals, HMO or not, in a defined zone) schemes. Licensing requirements, fees and conditions genuinely vary by council, so always check directly with your local authority for the property you're considering — don't assume national rules are the full picture.
Letting room-by-room usually brings in more total rent than letting the same property as one single-let tenancy, because every individual room is charged its own rent rather than one rent for the whole property. A five-bedroom house that might fetch £1,200 a month as a single-let could realistically bring in £2,500–£2,900 a month let room-by-room — a meaningful uplift in gross rental income from the same bricks and mortar.
This is the core attraction of the HMO model for investors: more income per property, which can translate into a noticeably higher gross yield than a comparable single-let in the same area.
The gap between gross and net yield is usually wider for an HMO than for a single-let, because of the additional costs involved: the HMO licence fee, higher landlord insurance premiums, fire safety equipment and certification, more frequent safety inspections and compliance paperwork, bills that landlords very commonly cover as part of an all-inclusive rent, a higher management or letting-agent fee to administer multiple separate tenancies, and increased maintenance wear-and-tear from having more occupants under one roof.
None of this means HMOs are a bad investment — it means the real comparison that matters is net yield, not just the headline gross rent, which is why this calculator deducts each of these costs explicitly.
A single-let property is either fully let or fully empty — one void period affects 100% of the rent. An HMO spreads that risk across multiple rooms, so one empty room while the rest stay occupied is a partial, not total, loss of income — which can make HMO income more resilient in some ways. In practice, though, individual rooms in an HMO often turn over more frequently than a whole single-let tenancy (particularly with younger, more transient tenant profiles), so total void days across the year can still be higher. A void allowance in the 8–12% range is a common starting point, adjusted for your local market and tenant type.
An Article 4 Direction is a planning tool used by local councils to remove permitted development rights in a defined area — most commonly used to stop houses being converted into small HMOs without planning permission. Many councils with a high concentration of existing HMOs, often around universities or in areas with strong house-share demand, have an Article 4 Direction in place covering some or all of their borough. If a property you're considering sits inside an Article 4 area, converting it into an HMO requires a full planning application rather than happening automatically — check with the local planning authority before assuming a conversion is straightforward.
An ordinary dwelling let to a single household falls under use class C3 (dwellinghouses). A small HMO — occupied by between 3 and 6 unrelated people sharing facilities — normally falls under use class C4 (houses in multiple occupation). Where there's no Article 4 Direction in place, converting a C3 property into a C4 small HMO is usually permitted development and doesn't need a separate planning application. Larger HMOs with 7 or more occupants fall outside C4 entirely, into a "sui generis" (unique) use class, and normally require planning permission from the council regardless of any Article 4 Direction.
HMOs are subject to materially stricter safety requirements than single-lets, set out in the Management of Houses in Multiple Occupation (England) Regulations and reinforced through licence conditions. Typical requirements include interlinked smoke alarms on every floor (and heat alarms in kitchens), fire doors to escape routes, clearly signed and unobstructed means of escape, annual gas safety checks, periodic electrical installation condition reports (EICRs), and — for larger or higher-risk HMOs — emergency lighting and additional fire-stopping measures. Councils can and do inspect HMOs, and non-compliance can result in licence refusal, civil penalties of up to £30,000, or prosecution.
Take a £280,000 five-bedroom house. Let as a single-let at £1,200 a month, it would produce gross annual rent of £14,400 — a gross yield of 5.14%. Let instead as an HMO at an average of £550 per room per month across 5 rooms, it produces gross annual rent of £33,000 — a gross yield of 11.79%, more than double. After typical HMO running costs (an 8% void allowance, £6,000 of bills included in the rent, a £1,200 annual licence cost, a 10% management fee, and £1,500 of maintenance and insurance), net annual income comes to £18,624 — a net yield of 6.65%. Even after all those extra costs, the HMO still clears a meaningfully higher yield than the single-let's gross figure, let alone its own net figure after costs.
Standard buy-to-let mortgages are usually designed around a single tenancy and don't fit the HMO model well. Most lenders require a specialist HMO mortgage, where they'll typically look at the number of rooms/occupants, whether the property is licensed (or will need to be), and often your experience as a landlord. HMO mortgage rates, arrangement fees and minimum deposits are commonly a little higher than for an equivalent standard buy-to-let, reflecting the slightly higher perceived risk and management complexity lenders attach to multi-let properties.
There's no special tax regime just because a property is an HMO — rental profits are taxed as ordinary UK property income in the same way as any other let property. The Section 24 restriction on mortgage interest relief for individual landlords (which replaced full interest deductibility with a basic-rate tax credit) applies equally to HMOs and single-lets. Running costs specifically associated with the HMO — the licence fee, bills you pay on tenants' behalf, and furnishings for shared/communal areas — are normally allowable expenses or may qualify for capital allowances, so keep clear records of HMO-specific spending.
Where a property is licensed, councils apply mandatory national space standards: a single room used for sleeping by one adult must be at least 6.51m², and a room slept in by two adults must be at least 10.22m² (smaller rooms used only by a child under 10 have a lower 4.64m² minimum). Rooms below these thresholds cannot lawfully be counted as a sleeping room in a licensed HMO, and the council can require you to stop using an undersized room for sleeping. Always measure actual room sizes before assuming a given room count is achievable. If you're weighing up an HMO purchase against a standard buy-to-let, it's worth running the numbers through our buy-to-let mortgage calculator and comparing the result with our general rental yield calculator for a single-let on the same property.
The guidance used to build this calculator is drawn directly from UK government sources. For the full legal detail behind the figures above, see:
Comparing an HMO against other ways to hold or finance this property? These tools cover the rest of the picture, including the extra mortgage interest tax restriction landlords should factor into their net figures — see our Section 24 landlord tax calculator for how that affects an HMO held personally.