Before running any detailed model, there is a single calculation that tells you which way a market leans. It takes half a minute and it is remarkably good at flagging the extremes.
Price-to-rent ratio = home price / annual rent for an equivalent propertyA $450,000 house, where a comparable property rents for $2,200 a month, gives $450,000 ÷ $26,400 = 17.0.
#What the number means
Under 15 — buying is generally favourable. Rent is high relative to purchase prices, so the mortgage and carrying costs are covered comparatively quickly. Much of the US Midwest and South sits here.
15 to 20 — genuinely balanced. The decision turns on your specific circumstances: how long you will stay, your down payment, the mortgage rate available to you, and what else you would do with the cash.
Over 20 — renting is generally favourable. Purchase prices are high relative to the income the property can generate. Coastal US metros, London, Sydney, Vancouver and much of urban Canada frequently sit between 25 and 40.
Over 30 — the market is being priced on expected appreciation rather than on the value of the shelter it provides. Buying is a bet on future price growth, not a cost calculation.
#Why it works
The ratio is really a crude yield measure. Inverting it gives the gross rental yield: a ratio of 20 implies a 5% gross yield, and a ratio of 33 implies 3%.
Once you subtract property tax, insurance, maintenance and vacancy — conventionally 35% to 45% of gross rent — a 3% gross yield becomes a net yield below 2%. At that point the property only makes financial sense if it appreciates meaningfully, which is a forecast rather than a calculation.
#Comparing like with like
The ratio only means something if numerator and denominator describe the same property. Common errors:
Comparing a house price to an apartment rent. If you would buy a three-bedroom house but currently rent a one-bedroom flat, you are not comparing the same thing. Use the rent for the property you would actually buy.
Using city-wide medians. Neighbourhood variation within a metro can be enormous. Pull three or four actual rental listings for comparable properties on the same streets.
Ignoring what is included. If the rent includes utilities, parking or amenities, adjust the annual figure downward before dividing.
#Where the ratio misleads
It ignores mortgage rates entirely. A ratio of 18 at a 3% mortgage rate is a very different proposition from a ratio of 18 at 7%. The interest rate determines what fraction of your payment builds equity versus disappears.
It ignores rent growth. A market at 22 today, where rent rises 6% a year, converges toward buying much faster than a market at 22 with flat rents. This is the strongest structural argument for buying: a fixed mortgage payment is frozen while rent compounds indefinitely.
It ignores transaction costs and your time horizon. Even in a ratio-of-12 market, buying with a two-year horizon loses money once you pay 8% to 10% round trip to get in and out.
It ignores tax treatment, which varies enormously by country and, in the US, by whether you itemise.
#How to use it properly
Treat the ratio as a screen, not a decision.
If it comes out below 15, buying is probably sound provided you will stay long enough to clear transaction costs. If it comes out above 25, you need a genuinely compelling non-financial reason — stability, schools, a property you cannot rent — because the arithmetic is unlikely to favour you.
For everything in between, the ratio has done its job by telling you the answer is not obvious. That is when to run a full rent vs buy comparison with your actual down payment, mortgage rate, maintenance assumption and expected holding period.
#The number that overrides it
How long you will stay. In a ratio-of-12 market with a three-year horizon, renting still wins. In a ratio-of-28 market with a twenty-five year horizon and stable employment, buying may still make sense on rent-growth grounds alone.
Transaction costs are the reason. Roughly 8% to 10% of the property value disappears across a purchase and sale. Recovering that takes years in any market, and no ratio can shorten it.
Frequently asked questions
What is a good price-to-rent ratio?
Below 15 generally favours buying, 15 to 20 is balanced, and above 20 generally favours renting. These are screens rather than rules — mortgage rates, expected rent growth and your holding period all shift the outcome materially.
How do I find comparable rents?
Search current rental listings for properties of the same size, condition and neighbourhood as the one you would buy. Use three or four listings rather than one, and prefer active listings over historical data, which lags the market.
Does the ratio work outside the US?
The concept applies anywhere, but the thresholds need local calibration. Markets with different tax treatment, transaction costs or tenant protections sustain structurally different ratios without being mispriced.