Build vs Buy a House: 25-Year Cost Calculator 2026

How the build vs buy comparison works

A house has three costs and one winner at each step. The upfront is the price: for building, the land plus the construction; for buying, the purchase price. The 25-year gross is the upfront plus the 25-year upkeep. The net is the gross minus the resale value after 25 years. The winner at each step is the lower number — and a negative net means the house gained more value than it cost, so the more negative net wins.

At the defaults — build $430,000 ($80,000 land + $350,000 construction), buy $400,000, upkeep build $45,000 and buy $95,000, resale build $550,000 and buy $520,000 — the upfront is $430,000 against $400,000, so buy wins upfront by $30,000. The gross is $430,000 + $45,000 = $475,000 against $400,000 + $95,000 = $495,000, so build wins gross by $20,000. The net is $475,000 − $550,000 = -$75,000.00 against $495,000 − $520,000 = -$25,000.00, so build wins net by $50,000.00. Net per year is -$75,000 ÷ 25 = -$3,000.00 against -$25,000 ÷ 25 = -$1,000.00.

The worked example, line by line

Setup: land $80,000, construction $350,000, buy price $400,000, upkeep build $45,000 and buy $95,000, resale build $550,000 and buy $520,000, horizon 25 years.

Line 1 — the build price. $80,000 + $350,000 = $430,000 upfront to build, against $400,000 to buy, so buy wins upfront by $30,000.

Line 2 — the 25-year gross. Build: $430,000 + $45,000 = $475,000. Buy: $400,000 + $95,000 = $495,000. Build wins gross by $20,000, because the new house needs $50,000 less upkeep.

Line 3 — the net. Build: $475,000 − $550,000 = -$75,000.00. Buy: $495,000 − $520,000 = -$25,000.00. Build wins net by $50,000.00.

Line 4 — the net per year. Build: -$75,000 ÷ 25 = -$3,000.00 a year. Buy: -$25,000 ÷ 25 = -$1,000.00 a year. Both are negative, which means both houses gained more value than they cost — the build just gained $50,000 more.

Line 5 — the break-even prices. Building ties the buy net when the build price is $480,000.00: at $480,000 the build net is $480,000 + $45,000 − $550,000 = -$25,000.00, the same as buying. Buying ties the build net when the buy price is $350,000.00: at $350,000 the buy net is $350,000 + $95,000 − $520,000 = -$75,000.00, the same as building.

Every branch, checked

Build price $380,000: the upfront is $380,000, the gross is $380,000 + $45,000 = $425,000 and the net is $425,000 − $550,000 = -$125,000.00, so build wins net by $100,000.00. A cheaper build wins on every step at once: upfront, gross and net.

Buy price $350,000: the upfront is $350,000, the gross is $350,000 + $95,000 = $445,000 and the net is $445,000 − $520,000 = -$75,000.00, which is exactly the build net — so neither wins net, a tie. A $50,000 cheaper purchase price is exactly what buying needs to catch building.

Buy upkeep $150,000: the gross for buying rises to $400,000 + $150,000 = $550,000 and the net rises to $550,000 − $520,000 = $30,000.00 — a positive net, which means the bought house cost more than it returned — so build wins net by $105,000.00. An old house with a failing roof and boiler is the dearest house of all.

Resale $0 for both: with no resale at all, the net is the gross: build $475,000.00 against buy $495,000.00, so build still wins net by $20,000.00. Resale is not what makes building win here — the lower upkeep does.

Build $500,000, buy $450,000, upkeep $60,000 and $120,000, resale $600,000 and $560,000: the gross is $500,000 + $60,000 = $560,000 against $450,000 + $120,000 = $570,000, so build wins gross by $10,000. The net is $560,000 − $600,000 = -$40,000.00 against $570,000 − $560,000 = $10,000.00, so build wins net by $50,000.00. Even when building costs $50,000 more upfront, the cheaper upkeep and the stronger resale can still win the net.

Reverse — the break-even prices: building ties buying when the build price is $480,000.00, and buying ties building when the buy price is $350,000.00. Between those two prices, building wins net; outside them, buying does.

What the defaults assume

The model assumes a 25-year stay in one house: a shorter stay changes the upkeep and the resale, because the roof and the boiler may never need replacing. It assumes the upkeep figures cover repairs, a new roof, a new boiler and new windows over 25 years, and that the new build needs $45,000 of it against $95,000 for the older bought house. It assumes the resale values are what the houses sell for after 25 years, with no selling costs taken off — agent fees and closing costs come out of the resale in real life. It leaves out the mortgage interest, the property tax, the insurance, the moving costs and the rent you would pay while building — ask the lender and the builder whether the quotes include those. Rounding convention: money is rounded to cents, and all figures are computed from unrounded values, rounded only for display.

Output · formula · meaning

Who uses this

• The couple choosing between a plot and a listing: they learn building wins net by $50,000.00 at these prices — so they price the plot and the build before they fall in love with the listing, knowing the cheaper upfront is not always the cheaper house.
• The buyer who found a $350,000 house: they learn that price ties building exactly, at -$75,000.00 net each — so they know the decision is not about money any more, it is about the street and the schools.
• The owner of an old house with a failing roof: they learn upkeep of $150,000 turns the buy net positive at $30,000.00 — so they get the roof and the boiler quoted before they sign, because the upkeep is the whole comparison.
• The family planning to stay 25 years: they learn the net per year is -$3,000.00 for building against -$1,000.00 for buying — so they see the house as a place to live that also gained value, not as a bill.

Accuracy & limitations

The math is exact for the numbers you enter: the build price is the land plus the construction, the gross is the upfront plus the upkeep, and the net is the gross minus the resale. What the model cannot do is price your plot or your builder for you: get the land and the construction quoted, and get the bought house surveyed, because a $50,000 repair the survey misses is a $50,000 swing in the net. It leaves out the mortgage interest, the property tax, the insurance, the moving costs and the rent you would pay while building — ask the lender and the builder whether the quotes include those. It assumes the resale values are what the houses sell for after 25 years, with no selling costs taken off. For the mortgage on either house, see mortgage calculator; for renting instead, see rent vs buy home calculator; for building against buying a home in general, see build vs buy home.