The numbers behind a rental property purchase
Listings quote a yield, agents quote a cap rate, lenders ask for coverage, and your bank account only cares about cash flow. These are not competing measures; they answer different questions at different stages. This guide walks through them in the order an investor actually uses them, from a thirty-second screen to the decision, with the calculator for each.
1. The screen: gross rent multiplier
With a long list of listings, you need a number that takes two inputs and sorts them. The gross rent multiplier is price divided by annual rent: how many years of gross rent it takes to add up to the price. A lower multiplier means more rent per unit of price. It ignores every cost, so it only decides which properties deserve a closer look. The gross rent multiplier calculator gives the multiplier, the gross yield and the monthly rent-to-price ratio, and works back from a target multiplier to a price.
2. The income: vacancy and operating expenses
Everything after the screen depends on getting net operating income right, and most quoted figures get it wrong by using full rent and leaving costs out. Start with the rent, take off a vacancy allowance even if the property is let today, then subtract the costs of running it: property tax, insurance, maintenance, management, utilities you pay and a reserve for the roof and the boiler. The vacancy rate calculator turns empty units into lost rent, and the rental cash flow calculator applies vacancy and expenses to monthly rent. What is left before the mortgage is net operating income.
3. The return on the property: cap rate
The capitalisation rate is net operating income divided by price. It strips financing out and asks what the property earns on its price if bought for cash, which makes properties comparable regardless of how each buyer borrows. A higher cap rate means more income per unit of price and usually more risk. There is no universal good number; compare with recent sales of similar properties nearby. The cap rate calculator builds NOI from rent, vacancy and expenses, and turns a target cap rate into the price you should pay for the same income, which is the figure to negotiate from. Investors outside North America often use gross and net yield instead; the rental yield calculator gives both.
4. The mortgage: payment and coverage
Financing changes the picture in two ways. First, the payment: the business loan calculator turns loan amount, rate and term into the monthly payment and total interest, and its affordability mode shows the largest loan a payment supports. Second, the lender's test: the debt service coverage ratio is NOI divided by a year of loan payments, and lenders want it above a threshold of their own, often somewhere above 1.2. The DSCR calculator gives the ratio and the largest payment a target ratio allows. If the deal only works with a loan the coverage ratio will not support, it does not work.
5. The return on your money: cash on cash
Once the mortgage is in, the question becomes what the cash you actually invested earns. Annual cash flow after the mortgage divided by the deposit, closing costs and initial repairs is the cash on cash return. It can be higher or lower than the cap rate depending on the interest rate; when borrowing costs more than the property earns, leverage works against you. The cash on cash return calculator gives the return and the years of cash flow it takes to get your cash back. A negative figure means the property costs you money each year; that can be a deliberate bet on appreciation, but it should be deliberate.
6. The monthly reality: cash flow
All of the above are annual ratios. What you live with is the monthly figure: rent minus vacancy, minus expenses, minus the mortgage. The rental cash flow calculator shows it per month and per year, with the expense ratio as a check that costs are complete. A property that produces a small positive cash flow in a good month will produce a negative one when the boiler fails, so judge it against a reserve, not against zero.
How the numbers connect
Price and rent give the multiplier. Rent, vacancy and expenses give NOI. NOI over price is the cap rate. NOI over loan payments is coverage. NOI minus loan payments is cash flow, and cash flow over cash invested is cash on cash. Change one input and every figure moves, which is why a single all-in-one calculator can hide which assumption is doing the work. Running the steps separately shows where a deal is strong and where it is being carried by an optimistic rent or a missing cost.
After the purchase
The same arithmetic runs every month once you own the place. Rent increases need to be weighed against the vacancy a move-out causes; the rent increase calculator shows the trade-off. Partial months at move-in and move-out are handled by the prorated rent calculator. The Landlord Rent & Expense Tracker keeps the rent log, late payments, expenses and yield per property in one workbook so that next year's numbers come from records rather than memory.