Free Home Renovation Calculator (+ Guide)

What is a home renovation calculator?

A home renovation calculator adds up every cost of renovating a home, from the general contractor's quote to the windows and permits.

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.

HUD's contingency rules, in full

HUD's 203(k) renovation loans set the contingency, "funds that are set aside to cover unforeseen project costs," by the home's age.

• Under 30 years old: up to the lender, with a maximum of 20%, and 10% to 20% when there's termite damage
• 30 years or older: 10% to 20% of the repair costs
• 30 years or older, with the utilities not working: 15% to 20%

The calculator's contingency choices follow the same range, from none to 20%.

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 1,800 sq ft home with 3 quotes of $85,000, $96,000 and $90,000, plus design, windows, flooring, paint and permits, and a 20% contingency for an older house.

The cheapest quote is $85,000, $11,000 less than the dearest. Your other costs add $28,500, so the project comes to $113,500 before the contingency.

A 20% contingency adds $22,700, for a total of $136,200. That's $75.67 per square foot, and $3,800 left of a $140,000 budget for the renovation.

Mistakes to avoid

These are the slips that come up most.

• Starting with the finishes before the roof, wiring and plumbing
• Leaving no contingency on an older home
• Signing a contract with blank spaces, which the FTC warns against

Who is the home renovation calculator for?

It's for anyone renovating a home they own or just bought, and these tools help around it.

• Roofing calculator – for the roof
• Siding calculator – for the walls outside
• Home equity loan calculator – if you borrow for it

Price the house as one project, and each room's choices get easier.