BTL Yield Calculator

Understanding buy-to-let yields

A yield is just the annual return from rent expressed as a percentage of the property's value. But there are several different ways to calculate it — and the difference matters enormously when evaluating whether a deal stacks up.

Gross yield

Gross yield is the simplest measure: annual rent divided by property price, expressed as a percentage. It ignores all costs — void periods, maintenance, insurance, management fees, and mortgage payments. Its only real use is for quick, like-for-like comparisons between properties. A property with a 6% gross yield is not necessarily better than one with a 5% gross yield once costs are factored in.

The standard industry calculation uses the full 12 months of rent, not void-adjusted rent. This calculator does the same for gross yield so your numbers are comparable with estate agent listings and market data.

Net yield

Net yield deducts the ongoing operating costs — management fees, maintenance and insurance — but typically excludes mortgage payments. It answers the question: "how efficiently is this property generating income relative to its value?" Net yields of 4–6% are typical in many UK cities; London properties often yield 3–4% net.

Cash flow — the number that really matters

Monthly cash flow is what lands in your bank account (or doesn't) each month after all outgoings including the mortgage payment. A property can have a healthy gross yield but still generate negative monthly cash flow if the mortgage is large and interest rates are high.

Many landlords who bought with cheap mortgages in the 2010s found their properties went cash-flow negative when rates rose sharply in 2022–23. Cash flow is the most practical measure of whether a BTL investment works month to month.

Void periods

Voids — periods when the property is empty — are one of the most significant but often underestimated costs. Even one or two weeks per year reduces your effective annual income by 2–4%. In reality, voids can be longer between tenancies, during refurbishments, or if a tenant defaults. The calculator lets you model this directly.

Section 24: the tax landlords need to understand

Before 2017, landlords could deduct mortgage interest from their rental income before calculating tax. Section 24 of the Finance Act 2015 changed this fundamentally. Since April 2020, the deduction has been replaced by a 20% tax credit on mortgage interest — regardless of whether you pay 20%, 40% or 45% income tax.

For a basic-rate taxpayer, the impact is roughly neutral. For a higher-rate taxpayer, the effective cost of the mortgage interest is significantly higher under Section 24 — in some cases pushing landlords into losses even where the cash flow appears positive.

Owning BTL properties via a limited company is not affected by Section 24, which is why many higher-rate taxpayer landlords have restructured their portfolios into limited companies. However, this creates additional accounting and tax costs and may trigger Stamp Duty Land Tax on the transfer.

Capital appreciation vs income

Yield calculations only capture the income return from a BTL property. Capital appreciation — the increase in property value over time — is an entirely separate consideration. UK house prices have historically risen over the long term, but this is not guaranteed and varies enormously by location. A property with a low yield in a high-growth area may ultimately deliver a better total return than a high-yield property in a stagnant market.

Running costs to budget for

• Letting agent fees: typically 8–15% of rent for full management, 1–3 months' rent for tenant find only.
• Maintenance and repairs: a common rule of thumb is 1% of property value per year, though this varies widely.
• Landlord insurance: buildings insurance, contents (if furnished) and landlord liability cover. Typically £200–£700 per year.
• Ground rent and service charges: applicable to leasehold properties — can be significant on flats.
• Safety certificates: gas safety (annual), electrical inspection (every 5 years), EPC.
• Accountancy: especially if operating through a limited company.