How the calculations work
OKRoomTools turns measurements and the product information you enter into preliminary shopping quantities and project budgets. Check the examples below, and confirm your product and site requirements before ordering.
Flooring sold by the box
Add the net area of the rectangular sections using the same product. Multiply by 1 + allowance percentage / 100, divide by the manufacturer’s coverage per box, then round up to whole boxes.
Example: a 16 × 12 ft room plus a 10 × 4 ft hallway is 232 ft². A 10% allowance makes 255.2 ft². At 24 ft² per box, you need 11 boxes, covering 264 ft². At $37 per box plus $22 accessories and $25 delivery, the purchase costs $454.
You can enter a price per box or a price per ft²/m². Area pricing applies to the full area of whole boxes purchased, not just the net room area. For example, at $2/ft² those 264 ft² cost $528 before accessories and delivery, even though the net room area is 232 ft². The material purchase total is rounded to cents once.
The 8.8 ft² above the allowance is an arithmetic surplus, not a guarantee of reusable offcuts. Different products and batches must be ordered separately. This box calculator does not count individual tiles or optimize cutting patterns.
For irregular floor areas, split the floor into rectangles without counting any section twice. Check the installer’s allowance and the coverage printed on the actual package.
Paint for all coats
For each separate rectangular room, wall area = 2 × (length + width) × height, minus the total openings you enter. Add length × width if you include that ceiling. Required paint = total paintable area × coats ÷ coverage per coat × (1 + allowance percentage / 100).
For an L-shaped or open-plan space, individual walls, or a surface already measured, choose Known paintable area. Enter the actual surface after subtracting openings, and include any ceiling only if you intend to paint it with the same product. In this mode OKRoomTools uses your area directly: it does not subtract openings again or add a ceiling automatically.
Do not split an L-shaped space into imaginary enclosed rooms for the paint calculation: their perimeters would invent walls along the shared edges. Measure the real wall faces, count each face once, and enter their net paintable area. Use separate calculations or projects for different products and colors.
Example: a 16 × 12 × 8 ft room has 448 ft² of walls. Subtract 42 ft² of openings to get 406 ft². With two coats, illustrative coverage of 400 ft² per US gallon and 5% extra, you need 2.1315 US gallons. Using only one-gallon cans means buying three cans. Three $42 cans plus $12 accessories cost $138.
The coverage in this example is illustrative, not a universal paint specification. Texture, porosity, color changes, tools and application affect consumption. Use the manufacturer’s coverage for your product. All entries in the current calculation share the same product, color, coat count and coverage; plan primer, different colors and different ceiling paints in separate calculations. Comparing can sizes does not optimize a mixture of can sizes.
US gallons and imperial gallons are different units. 1 US gallon is 3.785411784 liters; 1 imperial gallon is 4.54609 liters. OKRoomTools converts measurements and displayed coverage; changing the currency label does not apply an exchange rate.
Purchase costs and project budgets
Material costs use the whole boxes or cans you need to buy, plus the accessories and delivery entered for that option. Labor = hours × internal hourly cost. Custom items use quantity × internal unit cost; they can cover preparation, primer or other work and materials. Labor-only projects are supported without a material purchase. Add each cost once, avoiding amounts already included in another option or custom item.
Markup is a percentage of cost: $120 cost with 20% markup becomes $144. Margin is a percentage of the final price: $120 ÷ (1 − 0.20) becomes $150. They are different pricing methods. Money is calculated in cents; calculated fractional cents round to the nearest cent.
Choose Customer estimate to export the work scope and total before tax without the calculated internal costs or markup/margin breakdown. Choose Internal budget for the cost breakdown and pricing calculation. Your own notes and descriptions are included as entered, so review them before sharing either document.
Choose US Letter or A4 for the downloaded PDF. Browser printing uses the paper size selected in the print dialog. Optional business/contact details, reference and validity date describe the document you create; they are not verified by OKRoomTools. Project figures use your entered prices, not local market quotations. Taxes, product suitability, cutting layouts and structural design are not calculated.
Sources and checking your inputs
These references explain practical measurement and coverage considerations. They do not certify OKRoomTools or guarantee a result.
- EGGER: waste allowance for specific flooring and installation conditions
- BEHR: paint coverage and estimating limitations
- Lowe’s: room dimensions, openings and product coverage
- Inch Calculator: floor measurements and waste allowance
- Inch Calculator: individual tiles, package coverage and layout considerations
Formulas and worked examples last checked on October 23, 2026. This is a documented calculation method, not a claim of professional site inspection or independent certification.