US Flag Size Calculator (official 1 : 1.9 proportions, union, stripes & stars)

Understanding the US flag size calculator — concept and principle

This calculator gives every dimension of a United States flag in the official proportions from the height (hoist) or the length (fly): the size of the blue union, the stripe width, the star diameter and the star spacing. Use it to make a flag, design a banner or graphic, or check whether a flag you own follows the standard shape.

Every part is a fixed fraction of the hoist (height).

How it is calculated

Executive Order 10834 (1959) sets each dimension as a multiple of the hoist A = 1.0:

Fly B = 1.9
Union hoist C = 0.5385 (7/13) and union fly D = 0.76
Star spacing E = F = 0.054 (vertical) and G = H = 0.063 (horizontal)
Star diameter K = 0.0616 and stripe width L = 0.0769 (1/13)

If you enter the fly, the hoist is first found as fly ÷ 1.9. Results are in the same unit you entered.

The principle

The design is a fixed shape that can be scaled to any size, so every part is a fixed fraction of the height. The flag has 13 equal horizontal stripes, alternating red and white, so one stripe is 1/13 of the hoist. The union covers the top seven stripes, which is why its height is 7/13 of the hoist. The 50 stars sit in nine rows that alternate six and five stars, spaced by E, F, G and H. The overall ratio of 1 : 1.9 is the official standard for flags made for federal agencies.

Worked example

Default inputs: hoist 90 (any unit).

Fly = 90 × 1.9 = 171.
Union hoist = 90 × 7 ÷ 13 = 48.46; union fly = 90 × 0.76 = 68.4.
Stripe width = 90 ÷ 13 = 6.92.
Star diameter = 90 × 0.0616 = 5.54.
Star spacing: vertical 90 × 0.054 = 4.86, horizontal 90 × 0.063 = 5.67.

Each point is the calculator re-run with only “Size (any unit: cm, in or ft)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Size (any unit: cm, in or ft)	Fly (length)
22.5	42.75
45	85.5
67.5	128.25
90	171
112	213.75
135	256.5
180	342

How to read the result

These are the official proportions. Many flags sold for homes and businesses use other shapes, such as 3 × 5 ft (1 : 1.67) or 4 × 6 ft (1 : 1.5), and they are still widely flown. If you are matching an existing flagpole bracket or a frame, measure the flag you have. For printing or sewing, add seam or bleed allowances to the finished sizes.

Common mistakes

Assuming every US flag is 1 : 1.9; commercial sizes are often shorter.
Making the union cover six or eight stripes instead of seven.
Measuring star spacing from star edges instead of star centres.
Forgetting to add hems or a heading strip when sewing.

Keep in mind: The proportions are from the executive order for federal flags. Display rules and etiquette are covered separately in the US Flag Code.

Frequently asked questions

What are the official US flag proportions?

Height 1.0 to length 1.9, with the union 7/13 high and 0.76 long.

Why is a 3 × 5 ft flag not 1 : 1.9?

Commercial sizes follow common fabric and pole sizes rather than the federal ratio.

How wide is each stripe?

One thirteenth of the flag's height.

Sources: Executive Order 10834 (1959), "Proportions and sizes of flags and position of stars", notes to 4 U.S.C. § 1 · 4 U.S.C. § 1 (thirteen horizontal stripes, alternate red and white)

Checked 9 Nov 2026. Executive Order 10834 (1959), “Proportions and sizes of flags and position of stars”, standard proportions A–L, as printed in the notes to 4 U.S.C. § 1 (U.S. Code, govinfo.gov); 4 U.S.C. § 1: thirteen horizontal stripes, alternate red and white.

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