US Flag Calculator - Official Proportions & Star Layout
Enter any one dimension and get every official U.S. flag measurement from Executive Order 10834, drawn on a live dimensioned blueprint.
For sewing, printing, woodworking or checking whether a flag follows the official government specification. All eight spec letters (A to L) update live on the blueprint below.
US Flag Calculator - Official Proportions & Star Layout
Enter any one dimension and get every official U.S. flag measurement from Executive Order 10834, drawn on a live dimensioned blueprint.
Which dimension do you know?
Quick values:
Unit
Dimensioned blueprint
The flag drawn to the exact official proportions, with the spec letters and your live values on engineering-style dimension lines.
About the US flag calculator
The exact geometry of the United States flag is set by Executive Order 10834, signed by President Eisenhower in 1959 when Hawaii's star was added. The order defines everything relative to the hoist (the flag's height, letter A): the fly is 1.9 times the hoist, the union (the blue canton) is 7/13 of the hoist tall - exactly seven stripes - and 0.76 of the hoist long, each of the 13 stripes is 1/13 of the hoist, and every star has a diameter of 0.0616 of the hoist.
The star field is a precise grid, not a scatter: the union is divided into 10 equal vertical spaces and 12 equal horizontal spaces, and the 50 stars sit on the crossings - nine rows that alternate six and five stars, which is why the rows appear staggered. One point of every star faces straight up.
Here is the surprise most people meet first: the common store-bought 3×5 ft flag does not follow the official ratio. A government-spec flag with a 3 ft hoist would be 5.7 ft long (3 × 1.9). The official 1.9 ratio is mandatory for flags made for the federal government; commercial flags commonly use 3:5 or 2:3 instead, which is why their unions and stars are also proportioned slightly differently. This calculator always applies the official ratios, so you can start from any single measurement - a stripe you want 2 inches wide, a star patch you already own, or the height of the wall you are decorating - and derive every other dimension exactly.
US flag dimension examples
Four ways to start from one known measurement.
| Known dimension | Result | Notes |
|---|---|---|
| Hoist A = 13 in | Fly 24.7 in, union 7 × 9.88 in, stripe 1 in, star 0.8008 in | A 13-inch hoist makes every stripe exactly 1 inch - handy for checking the ratios. |
| Stripe width L = 2 in | Hoist 26 in, fly 49.4 in, star 1.6016 in | Working backward from the stripe you want to sew. |
| Hoist A = 3 ft | Official fly 5.7 ft - not 5 ft | The store-bought 3×5 flag is a commercial ratio, not the government spec. |
| Star diameter K = 5 cm | Hoist 81.169 cm, fly 154.221 cm | Scaling a whole flag from a star patch you already have. |
How to use the US flag calculator
- Pick which dimension you already know - the flag height, its length, one stripe, a star, or the union.
- Enter the measurement and choose the unit (inches, feet, centimeters or meters).
- Read every official dimension in the results table; the Ratio column shows the exact rule from the executive order.
- Check the blueprint: each dimension line is labeled with its spec letter and your live value.
- Use the star-spacing values E and G to lay out the 50-star grid when sewing or printing.
US flag proportions FAQ
What are the official proportions of the US flag?
Relative to the hoist A: fly B = 1.9 A, union height C = 7/13 A, union length D = 0.76 A, stripe width L = 1/13 A, star diameter K = 0.0616 A. They are defined in Executive Order 10834 (1959).
Is a 3×5 ft flag official?
No. The official length of a flag with a 3 ft hoist is 5.7 ft. The 3:5 shape is a common commercial ratio; only flags made for the federal government must follow the 1.9 ratio.
How are the 50 stars arranged?
Nine horizontal rows alternating 6 and 5 stars. The union is divided into 10 equal vertical and 12 equal horizontal spaces, and stars sit on the grid crossings, producing the staggered pattern. One point of each star faces up.
How wide is each stripe?
Exactly 1/13 of the hoist - seven red stripes and six white ones. The union is seven stripes tall, which is why its height is 7/13 of the hoist.
What size are the stars?
Each star's diameter is 0.0616 of the hoist. On a government-spec flag with a 3 ft hoist that is about 2.22 inches.
Can I scale a flag from just one measurement?
Yes - that is what this tool does. Every official dimension is a fixed multiple of the hoist, so any single known dimension determines all the others exactly.