Quick answer
Room area = length × width. A 12 × 10 ft room is 120 ft², which is 13.33 square yards or 11.15 square metres.
Enter the length and width. The calculator returns the area in square feet, square yards and square metres.
Related tools: Wall Area Calculator: Wall area of a rectangular room after openings. Appliance Energy Cost Calculator: Electricity cost of running an appliance. Lighting Lumens Calculator: Lumens needed for a room at a light level you choose.
How to use the Room Area Calculator
- Enter length (ft) (above 0).
- Enter width (ft) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Length | A number, in ft | > 0 |
| Width | A number, in ft | > 0 |
Formula and method
Formula
area = length × width
IEEE-754 double precision; shown to the decimals indicated.
Also shown in square yards and square meters.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Length = 12; Width = 10.
| Result | Value |
|---|---|
| Room area | 120 ft² |
| Square yards | 13.33 |
| Square meters | 11.15 |
Example 2
Inputs: Length = 15.5; Width = 11.25.
| Result | Value |
|---|---|
| Room area | 174.38 ft² |
| Square yards | 19.38 |
| Square meters | 16.2 |
Example 3
Inputs: Length = 20; Width = 20.
| Result | Value |
|---|---|
| Room area | 400 ft² |
| Square yards | 44.44 |
| Square meters | 37.16 |
The first line is the headline result (room area). Below it the room Area Calculator lists square yards and square meters, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Why three units
Flooring is often sold by the square foot or yard and by the square metre outside the US. Seeing all three avoids conversion errors.
Irregular rooms
For L-shaped rooms, split the room into rectangles, calculate each and add them. Add 5 to 10% for waste when ordering flooring.
How the result changes with length
Holding every other input at the first worked example, this table changes only length. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Length | Room area | Square yards | Square meters |
|---|---|---|---|
| 6 | 60 ft² | 6.67 | 5.57 |
| 12 | 120 ft² | 13.33 | 11.15 |
| 24 | 240 ft² | 26.67 | 22.3 |
| 48 | 480 ft² | 53.33 | 44.59 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Length: entering "0" shows "Length must be greater than 0." beside that field and no result.
- Width: left empty shows "Enter width." beside that field and no result.
Choosing between the Room Area Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Wall Area Calculator](/lifestyle/wall-area-calculator/) | room length, room width and ceiling height | Wall area |
| [Appliance Energy Cost Calculator](/lifestyle/appliance-energy-cost-calculator/) | power, hours used per day and electricity price | Cost per day |
| [Lighting Lumens Calculator](/lifestyle/lighting-lumens-calculator/) | room area and target light level | Lumens needed |
| [Pool Fill Time Calculator](/lifestyle/pool-fill-time-calculator/) | pool volume and flow rate | Fill time |
| [Water Bill Calculator](/lifestyle/water-bill-calculator/) | water used, rate per unit and fixed monthly charge | Estimated bill |
Assumptions and limitations
- Irregular rooms need splitting into rectangles
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for length and width to confirm this.
Frequently asked questions
How do I measure a room?
Measure the longest wall-to-wall length and width.
Do I include closets?
Add them as separate rectangles.
How much extra flooring?
Add 5 to 10% for waste and cuts, more for diagonal patterns.
What does the Room Area Calculator calculate?
Floor area of a rectangular room. It returns Room area, Square yards and Square meters.
What formula does the Room Area Calculator use?
area = length × width. Also shown in square yards and square meters.
What do I need to enter in the room Area Calculator?
You enter Length (ft) and Width (ft).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Irregular rooms need splitting into rectangles.
What is an example of a room Area result?
With length 12 and width 10, the room area is 120 ft².
Where does the method come from?
The method follows: OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem; NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B (1 ft2 = 0.09290304 m2 exactly).
Related calculators
- Wall Area Calculator — Wall area of a rectangular room after openings.
- Appliance Energy Cost Calculator — Electricity cost of running an appliance.
- Lighting Lumens Calculator — Lumens needed for a room at a light level you choose.
- Pool Fill Time Calculator — Hours to fill a pool at a flow rate.
- Water Bill Calculator — Water bill from usage, rate and a base charge you enter.
- Water Usage Calculator — Household water use from people and use per person.
Sources
- OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B (1 ft2 = 0.09290304 m2 exactly)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.