Work out the monthly principal & interest on a mortgage. Enter the loan amount, annual interest rate and term in years.
This is principal & interest only. Your full monthly payment may also include property tax, insurance and HOA/service charges. Use the cash flow calculator to see the rental's net profit.
The monthly principal & interest uses the standard amortization formula: M = P·r·(1+r)ⁿ ÷ ((1+r)ⁿ−1), where P is the loan, r the monthly rate (annual ÷ 12) and n the number of months. Early payments are mostly interest; later ones mostly principal.
Principal and interest (P&I). It does not include property tax, building insurance or service charges, which vary by location — add those separately for your true monthly cost.
A longer term lowers the monthly payment but increases total interest paid. A shorter term costs more per month but far less interest overall.
Yes — the math is the same. Many buy-to-let loans are interest-only, in which case the monthly cost is simply loan × rate ÷ 12.
RentFlow pairs your mortgage cost with rent and expenses to show real per-property cash flow and yield. Free to start.
Get RentFlow — App StoreMore calculators: Rental Yield Calculator · Rental Cash Flow Calculator · Rent Increase Calculator & Legality Checker · Prorated Rent Calculator · Late Rent Fee Calculator · Cash-on-Cash Return Calculator · 1% Rule Calculator · Security Deposit Calculator · Gross Rent Multiplier (GRM) Calculator · Net Operating Income (NOI) Calculator · Rent-to-Income Ratio Calculator · Vacancy Rate Calculator · Operating Expense Ratio (OER) Calculator
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