Buy-to-Let Mortgage Calculator

Lenders lend on rent, not income — rent must cover a stressed payment (typically 125–145% at ~5.5–8.5% depending on product and taxpayer status).

Lender stress rate — usually ~5.5% for 5y fixes, higher for trackers/2y

Result

Max loan (rent-stressed)£200,000.00
Max LTV possible80%
Deposit needed at 75% LTV£62,500.00
75% loan (£187,500.00) passes ICR?Yes — covers 1.63× stressed payment
Est. monthly payment£866.67
Net cash flow / mo£533.33
Gross yield6.72%

How it's calculated

  1. 1

    Required stressed cover = 1.45× at 5.5% → max monthly interest = £965.52

  2. 2

    Max interest-only loan = £965.52 ÷ (5.5% ÷ 12) = £210,658.31

  3. 3

    Check the loan also fits 75–80% LTV — lender cap whichever is lower

Buy-to-Let Mortgage Calculator — FAQs

What is rental cover / ICR?

Lenders require rent ≥ 125–145% of a *stressed* monthly interest payment — basic-rate taxpayers typically 125%, higher-rate 145%.

What is the stress rate?

Not the pay rate — an assumed rate lenders test affordability at, usually ~5.5% for 5-year fixed products and up to ~8.5% for trackers or 2-year fixes.

How much can I borrow on BTL?

Min of the rental-cover cap and 75–80% LTV. On £1,400/mo rent at 145% cover and 5.5% stress: ~£210k.

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