Free US Flag Dimensions Calculator

Mastering American Flag Proportions with the US Flag Dimensions Calculator

Designing an accurate American flag requires strict adherence to the dimensional ratios set forth in Title 4 of the United States Code. The US flag size calculator streamlines this process: after you input any one measurement — either the hoist (height) or the fly (width) — the tool instantly computes the complete set of flag dimensions, including the union, stripes, and stars. This makes it an essential resource for craftspeople, event planners, and anyone who wants to produce a correctly proportioned American flag.

Official Ratios Defined by Federal Law

The flag’s layout is built on a few key proportions, with A representing the hoist (height) and B the fly (width). The following table summarizes the elements and their relationships:

Element	Symbol	Ratio (in terms of A or B)	Numerical multiplier
Hoist (height)	A	1.0	1 × any given height
Fly (width)	B	1.9	1.9 × A
Union height	C	$\dfrac{7}{13}$ of A	0.5385 × A
Union width	D	$\dfrac{2}{5}$ of B	0.7600 × B
Vertical star spacing	E	$\dfrac{1}{10}$ of C	0.0538 × C
Horizontal star spacing	F	$\dfrac{1}{12}$ of D	0.0633 × D
Star diameter	G	$\dfrac{4}{5}$ of stripe width (H)	0.0616 × A
Stripe width	H	$\dfrac{1}{13}$ of A	0.0769 × A

Each stripe occupies exactly one‑thirteenth of the hoist, while the union (the blue canton) spans seven stripes, hence its height is $\frac{7}{13}$ of A. The union width equals two‑fifths of the fly. The stripes alternate red and white, beginning and ending with red. Within the union, stars are arranged in alternating rows of six and five, with vertical and horizontal spacing derived from the union’s own height and width.

How the Dimensions Calculator Works

To use the American flag dimensions calculator, you simply choose to enter either the height or the width you want. The tool then determines the missing base value using the fixed hoist‑to‑fly relationship (1:1.9). Once A or B is known, every other element is calculated by multiplying the respective ratio by that base.

For example, if you specify a height of 4 feet:

• Width B = 1.9 × 4 = 7.6 feet
• Stripe width H = 4 ÷ 13 ≈ 0.3077 feet
• Union height C = $\frac{7}{13}$ × 4 ≈ 2.1538 feet
• Union width D = 0.76 × 7.6 ≈ 5.776 feet
• Star diameter G = 0.8 × 0.3077 ≈ 0.2462 feet

If you prefer to work with absolute values and would like to see the scaling factor explicitly, the calculator offers a “Show proportion coefficient (x)” option. This reveals the multiplier used to convert the ratios to real‑world units.

Commonly Used Flag Sizes

While the calculator can produce any size that obeys the official proportions, certain dimensions are widely recognized for specific uses. The table below lists two popular benchmarks:

Purpose	Dimensions (ft)	Dimensions (cm)
Typical household flag	3 × 5	91.44 × 152.40
Casket (burial) flag	5 × 9.5	152.40 × 289.56

Note that the burial flag strictly follows the 1:1.9 ratio (because 9.5 ÷ 5 = 1.9), whereas the household flag commonly sold as 3×5 is slightly narrower than the code would dictate (a true 1:1.9 flag at 3 ft hoist would be 5.7 ft wide). The calculator, however, always applies the legal ratio, ensuring that any flag you design matches the federal standard.

Authentic Colors

Title 4 also defines the exact shades for the flag’s three colors. When manufacturing or painting, use these hexadecimal values:

• Red: #B22234
• White: #FFFFFF
• Blue: #3C3B6E

Respectful Display and Care

Beyond measurements, the flag code provides guidelines for proper handling. The flag should be illuminated if flown at night, should be kept dry unless made of all‑weather material, should never touch the ground, and should be stored folded in a triangle with the stars visible. When a flag becomes worn or faded, the recommended method of disposal is a dignified burning ceremony. Awareness of these customs completes the knowledge needed to honor the national symbol.