Land & Construction Loan Calculator
Building rather than buying means financing two things at once: a piece of land and a construction budget that does not exist yet. This estimates the permanent mortgage payment on the combined total, which is the figure you will live with once the build is finished.
How to use it
- Enter the land cost and your estimated construction cost.
- Enter your down payment, rate, and term.
- Read the monthly payment, total project cost, and total interest.
Construction financing works in two stages
The number here models the end state: a conventional amortising mortgage on land plus build cost, less your down payment. Getting there involves a stage this calculator does not model, and it is worth understanding because it affects cash flow substantially.
During construction, most lenders use a draw schedule. The loan is not disbursed at closing; funds are released in stages as work is inspected and completed — typically at foundation, framing, rough-in of mechanical systems, drywall, and final completion. You pay interest only on the amount drawn so far.
That produces a rising interest-only payment through the build. Early on you owe interest on the land and the first draw; by the end you owe interest on nearly the whole balance. On a $350,000 project at 7 percent, the interest-only payment climbs from a few hundred dollars a month to roughly $2,000 by completion. Over a twelve-month build the total interest carried during construction is commonly $10,000 to $15,000, and if you are also paying rent elsewhere, that period is the tightest part of the project.
At completion the loan converts to a permanent mortgage — either automatically under a construction-to-permanent loan with one closing, or through a separate refinance with a second set of closing costs. The single-close structure is usually worth paying slightly more for.
Why lenders treat land differently
Raw land is poor collateral. It generates no income, can be hard to value where comparable sales are scarce, and is expensive to foreclose on. Lenders price that risk directly.
A standalone land loan typically requires 20 to 50 percent down, carries a rate one to three points above a mortgage, and often runs on a short term with a balloon payment. Unimproved land with no road access or utilities sits at the harsh end of that range.
A combined construction loan is usually cheaper, because the finished house is much better collateral than the dirt. If you already own the land outright, its appraised value can often count toward your equity requirement, which sometimes eliminates the cash down payment entirely.
Budget the contingency, because the estimate will move
Construction cost estimates are systematically optimistic, and the reasons are structural rather than a matter of finding a better builder.
Site conditions are the biggest single risk and are largely unknown until excavation. Rock, a high water table, unstable soil requiring engineered footings, or unexpected fill can add tens of thousands before anything is built above grade. Utility connections are the second: a long run to the nearest tap, or a well and septic system in place of municipal service, is routinely a five-figure item that estimates prepared from a plan set omit.
Then there are the changes you will make yourself. Standing in a framed room and deciding the window should be larger is a normal part of building, and every such decision is a change order priced without competition.
Plan on a contingency of 10 to 20 percent of construction cost, at the higher end for an unfamiliar site or a custom design. Entering your build cost with that contingency already included gives a payment figure you can actually plan around. Lenders increasingly require this, and they are right to.
At a glance
| Models | Permanent mortgage on land plus construction, after down payment |
|---|---|
| Does not model | Interest-only draw period during the build |
| Recommended contingency | 10 to 20 percent of construction cost |
| Transmitted | Nothing |
Frequently asked questions
Does this include interest during construction?
No. It models the permanent mortgage after completion. During the build you pay interest only on funds drawn, which commonly totals $10,000 to $15,000 over a twelve-month project.
Why do land loans cost more than mortgages?
Land generates no income, is harder to value, and is expensive to foreclose on. Expect 20 to 50 percent down and a rate one to three points above a mortgage.
Can I use land I already own as the down payment?
Usually yes. Lenders will typically count the appraised value of land you own outright toward the equity requirement, which can remove the cash down payment.
How much contingency should I budget?
10 to 20 percent of construction cost. Site conditions and utility connections are the largest unknowns, and neither is fully knowable before excavation.
Read more
How loans actually work — Why your first payment is almost all interest, and why the term costs more than the rate.