How This Calculator Works
Net monthly cashflow is what's actually left in your pocket each month after every cost — not a percentage measure like yield. The formula: Net Cashflow = Effective Rental Income − Total Expenses, where effective income is your monthly rent minus a void allowance (for the weeks the property may sit empty between tenants), and total expenses covers mortgage, letting agent fees, maintenance provision, insurance, ground rent, service charge and any other running costs.
Cashflow Calculator FAQs
What's a realistic void allowance to use?
4–8% is typical for a standard AST let, depending on area and tenant demand. Short-term/SA lets usually carry higher effective void allowances because of turnover between bookings — model those separately with our SA/Airbnb Calculator.
Should I use my mortgage's interest-only or repayment figure?
Enter whatever your actual monthly mortgage payment is, whether interest-only or capital repayment — the calculator just takes the figure you pay each month. Use the Mortgage Calculator first if you need to work that payment out.
What's the difference between cashflow and rental yield?
Yield measures rental income against the purchase price as a percentage. Cashflow is the actual pounds left in your pocket each month after every cost, mortgage included — a property can show a strong yield on paper but still have negative cashflow once you account for a leveraged mortgage payment.
Does this include one-off costs like re-letting fees or redecoration?
No — this is an ongoing monthly view. If you want periodic costs like re-let fees or between-tenancy redecoration reflected, pro-rate them into a monthly figure and add them under Other Costs.
What should I do if my net cashflow comes out negative?
Check your rent against comparable local listings with the Rental Yield Calculator, review whether refinancing could lower the mortgage payment, or reconsider whether the numbers work for that specific deal before proceeding.
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