How the estimate is worked out
For each room the calculator multiplies length by width to get the area, then multiplies the area by the rate you enter for that room. The rooms are added together, the contingency is a percentage of that subtotal, and tax is charged on the subtotal plus contingency. The last line divides the whole budget by the total area, so you can compare it with a rate a firm quotes you.
Lengths can be typed in feet and inches, such as 12'6", or as decimals. Switch to metres and every figure already typed is converted, including your rates.
Why you enter the rates
We build quotations for interior firms, and the same wardrobe can be quoted at very different rates by two honest firms in the same town, because of the board, laminate, hardware and finish behind it. An average would look precise and be wrong for your home, so this tool does not show one. Use rates from quotations you have received, or from your own past jobs if you are the designer.
From estimate to quotation
A budget per room is a start. A quotation the client can approve lists the items inside each room with quantities, units and rates. Use the free interior quotation template for a one-off, or try Interior Quote to send a branded quotation your client can accept on a phone.
Questions
How do I calculate interior design cost per sq ft?
Multiply each room’s length by its width to get its area, multiply that area by the rate per sq ft for the finish you want, and add the rooms together. Add a contingency for site changes and the tax that applies. This calculator does those steps for you, room by room.
Why does this calculator not show an average price?
Because an honest average does not exist. The same 2BHK can cost three times as much depending on city, board and laminate, hardware and who builds it. A made-up average would mislead you, so the calculator uses rates you get from a designer or from your own past jobs.
Where do I get a rate per sq ft?
Ask two or three interior firms for their rate for the finish you want, or, if you are a designer, use the rate from a similar finished job. Use the same rate for rooms with the same scope and a different one where the scope differs, such as a kitchen.
What is a contingency and how much should I keep?
A contingency is money set aside for changes found on site, such as uneven walls or a client asking for an extra unit. Ten per cent is a common starting point; keep more for old buildings or a loose brief.
Can I use this for a 3BHK or an office?
Yes. Add a row for each room or zone, from a 1BHK to a whole office floor. Use metres if your drawings are in metres; the calculator converts what you have already typed.