Rent vs buy: the calculator math no one shows you

Almost every "rent vs buy" calculator on the internet is rigged toward buying. They assume your home appreciates 5% a year, rent rises 3%, and the only ownership costs are mortgage and property tax. None of that is honest. The real math is closer than most people realise, and the answer is rarely the one your parents or a real-estate agent gives you.

The two questions you're actually asking

"Should I rent or buy" hides two separate decisions:

1. Financial: which option leaves me wealthier in N years?
2. Lifestyle: which option matches how I want to live?

This post focuses on the financial side. The lifestyle answer (do you want to commit to a city for 7+ years, do you want to renovate, do you want flexibility) is yours alone.

The buyer's costs nobody mentions

Your monthly mortgage payment is not your monthly cost of ownership. Real cost includes:

• Mortgage P&I (Principal + Interest)
• Property tax (1 to 2.5 percent of home value annually in most US states)
• Home insurance ($800 to $2,500 per year typical)
• HOA fees if applicable ($200 to $800 per month)
• Maintenance reserve: budget 1 to 2 percent of home value per year. A $500k home = $5,000 to $10,000 per year for repairs you can't predict
• Mortgage insurance (PMI): if you put less than 20% down, often 0.5 to 1 percent of loan annually
• Closing costs at purchase: 2 to 5 percent of home price (typically not financed; comes out of cash)
• Selling costs when you exit: 6 to 8 percent of sale price (agent commission, transfer tax, prep work)

That last line is the one most people forget. To break even financially on a home, you need it to appreciate enough to cover that 6 to 8 percent exit cost on top of everything else.

The opportunity cost of the down payment

If you put $100,000 down on a house, you no longer have $100,000 to invest. Over 10 years, $100,000 invested at a 7% return becomes $197,000. That $97,000 of foregone investment growth is a real cost of buying. Honest calculators include it. Most don't.

The honest formula

To compare apples to apples, you need to model:

If you rent:

• Monthly rent (rising at expected rate)
• Renters insurance
• The down payment + closing costs you'd have used to buy, invested instead, growing at expected stock-market return
• The monthly difference between what you'd pay to own and what you pay to rent, also invested if it's positive

If you buy:

• Mortgage P&I + property tax + insurance + HOA + maintenance reserve
• Home appreciating at expected rate
• Equity built through principal payments
• Selling costs at exit

Compare net wealth at year N. The breakeven year is where buying overtakes renting on a wealth basis. For most US/UK markets in 2026, that's 7 to 10 years. Below 7 years, renting almost always wins. Above 10, buying usually wins. The 7 to 10 year window depends on the specific numbers.

What moves the breakeven point

Home appreciation rate

The single biggest input. The long-run US average is 3.5 to 4 percent nominal (about 0.5 to 1 percent real after inflation). If you assume 6% or above, you're being optimistic; if you assume 2 to 3 percent, you're being conservative. Use the actual long-run average for your specific market, not the last 5 years (which were unusual).

Stock-market return assumption

The opportunity cost of your down payment hinges on this. The long-run stock market real return is 6.5 to 7 percent. Use that, not 10% (which is the nominal return ignoring inflation).

Rent vs ownership cost ratio

If rent is much cheaper than the equivalent monthly cost to own, you have surplus cash to invest. If rent is roughly equal, ownership is more competitive. The classic rule of thumb: if total monthly cost to own is more than 1.3 times the monthly rent for a comparable property, renting is probably winning the math.

How long you'll stay

Selling costs make short ownership periods brutal. If there's any chance you'll move within 4 years (job change, family expansion, divorce, city you're not sure about), renting almost always wins.

The two cases where buying clearly wins

1. You will stay 10+ years and the local rent-to-price ratio favours ownership. Long horizon kills the selling-costs penalty and lets compounding home equity work.
2. The home is materially better than what you can rent. If renting equivalent to what you can buy is impossible (custom home, specific neighbourhood with no rentals), the math becomes secondary because you're choosing a thing you can't get otherwise.

The two cases where renting clearly wins

1. You'll stay less than 5 years. Selling costs eat your gains; the math is decisive.
2. You're in a high-cost-of-ownership city with strong rent-control. Cities like New York, San Francisco, London under right conditions: total ownership cost is 2 to 3 times equivalent rent. Investing the difference compounds dramatically.

FAQs

What's the "right" home appreciation rate to assume?

Long-run US average: 3.5 to 4 percent nominal. UK: similar. Don't extrapolate the last 5 years. Local markets can be hotter or colder; check Zillow / Land Registry data for your specific zip code over a 20-year window.

Does buying still make sense if interest rates are high?

Higher rates mean a higher mortgage payment, which raises monthly cost of ownership and shifts the breakeven year out. With 7% rates and 4% expected appreciation, buying often only wins if you stay 12+ years. With 4% rates and 4% appreciation, the breakeven shrinks to 6 to 8 years.

What about "throwing money away on rent"?

This phrase is the single most expensive misconception in personal finance. Mortgage interest, property tax, insurance, maintenance, opportunity cost of the down payment, selling costs: every one of those is "thrown away" too. Only the principal portion of the mortgage payment is building equity, and in the first 5 to 7 years that's a small fraction of each payment. Renting buys you flexibility and liquidity; owning buys you potential appreciation and a forced savings vehicle. Neither "throws money away."

To run your specific scenario with all the hidden costs included: the Rent vs Buy Calculator models 30-year wealth side-by-side, surfaces your exact breakeven year, and the AI coach explains which input is driving the result so you can stress-test your assumptions before signing anything.