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bythenumbers

Investing

Buy to let cash flow calculator

Whether a let leaves you cash each month after costs.

  • What it means

    This shows whether a buy-to-let property leaves you cash each month after the mortgage and running costs.

  • Why it matters

    A property can look fine on yield and still lose money each month once voids and bills are included.

  • When to use it

    Use it before you buy an investment, or when reviewing an existing rental against rising costs or rate changes.

  • How to read the result

    Positive monthly cash flow means rent covers the bills in this model. Tax on rental income is not included.

Your figures

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Methodology

Rules checked against published sources as of 2025-04-01.

  • Effective rent deducts void weeks from headline rent.
  • Cash flow is effective rent minus mortgage and the operating costs you enter.
  • Gross and net yield use purchase price as the denominator.

Pair the numbers with area intelligence for a postcode.

FAQs

Is tax included?

No. Personal tax on rental income is not modelled. Speak to a tax adviser for your position.