Free Basement Finishing Calculator (+ Guide)

What is a basement finishing calculator?

A basement finishing calculator adds up every cost of turning a basement into living space, from the contractor's quote to the egress window.

It shows the total with a contingency, the cost per square foot and what's left of your budget.

How it works

The cheapest of your quotes goes in the total, next to the costs it doesn't cover.

What the building code asks of a basement

The 2024 International Residential Code sets the rules most US towns build on, and a finished basement meets several of them.

• Every basement, and every bedroom in it, needs an emergency escape window or door (R319.1)
• Its opening must be at least 5.7 sq ft, 24 inches high and 20 inches wide, with the bottom no more than 44 inches above the floor (R319.2)
• Living space needs a ceiling of at least 7 feet (R313.1)

Your town may use another edition or its own changes, so ask its building department what applies.

How to compare contractors' quotes

The Federal Trade Commission gives this advice before you hire anyone.

• Hire only licensed and insured contractors, and check the license with your state or county
• Get several written estimates, each with the work, the materials, the completion date and the price
• Don't automatically pick the lowest bid, and ask why if the estimates differ a lot
• Get a written contract with the contractor's license number and the start and finish dates
• Never pay the full amount up front, and make the final payment only when the work is done

It also warns that a contractor who asks you to get the permits, or who only takes cash, may be running a scam.

How much contingency to add

A contingency is money set aside for what you find once the walls or the ground are open.

HUD requires one on its 203(k) renovation loans: 10% to 20% of the repair costs on a home 30 years or older, and at least 15% when the utilities don't work.

On a newer home, it's up to the lender, to a maximum of 20%.

A worked example

Here's the example the calculator loads: an 800 sq ft basement with 2 quotes of $38,000 and $42,000, plus an egress window, flooring, paint and permits.

The cheapest quote is $38,000, $4,000 less than the dearest. Your other costs add $9,500, so the project comes to $47,500 before the contingency.

A 10% contingency adds $4,750, for a total of $52,250. That's $65.31 per square foot, and $2,750 left of a $55,000 budget for the basement.

Mistakes to avoid

These are the slips that come up most.

• Finishing over a damp wall before fixing the water
• Forgetting the egress window the code asks for
• Finishing before asking the building department what it requires

Who is the basement finishing calculator for?

It's for anyone turning a basement into a room, an office or a rental, and these tools help around it.

• Flooring calculator – for the floor
• Paint calculator – for the walls
• Home equity loan calculator – if you borrow for it

Plan the water and the window first, and the rest of the basement follows.