Flag Sizes

This free tool shows flag sizes for a flagpole. Enter a pole height and it suggests a flag size, or enter a flag size and it suggests a pole height. It runs in your browser, nothing is uploaded, and no sign-up is needed.

The results come from two sources. The first is a rule of thumb from seller guides: the flag length should be between one quarter and one third of the pole height. The second is the size charts of two sellers, shown side by side. Sizes are given as hoist x fly in feet, for example 3 x 5.

Use the tool as a starting point, then check the sizes against your flag and your site. The two sellers do not always agree, so treat the output as a reference rather than a fixed answer.

How to use the Flag Size Calculator

1. Under “What do you know?”, choose “The flagpole height” if you already have a pole, or “The flag size” if you already have a flag.
2. If you chose the pole, type its height into “Flagpole height above the ground”. Pick the unit you measured in: ft, m, in or cm.
3. If the site is exposed to strong wind, tick “Windy or exposed site”.
4. Read the pole results: “Flag length for this pole, rule of thumb”, “Sizes in that range”, “Seller guide A says”, “Seller guide B says” and, when the box is ticked, “Windy site”.
5. If you chose the flag, pick a size from “Flag size (hoist x fly, ft)”. The list runs from 2 x 3 up to 30 x 50.
6. Read the flag results: “Pole height for this flag, rule of thumb”, “Seller guide A puts it at” and “Seller guide B puts it at”.
7. Check the table, which lists each size with the pole height it suits.
8. To compare with the official proportion, open More options and enter a value in “Flag height for the official proportion (ft)”. The result appears as “Flag at the official US proportion”.

The presets fill in the inputs for you. They are a 20 ft pole, a 25 ft pole, a 30 ft pole and a 3 x 5 ft flag. Pole heights under 4 ft or over 150 ft show a warning, and blank, zero or non-numeric heights show an error.

How does the rule of thumb turn a pole height into a flag size?

The rule of thumb says the flag length should be one quarter to one third of the pole height. Divide the pole height by 4 for the shortest length and by 3 for the longest, and the flag length falls between those two numbers.

For a 20 ft pole, the range is 5 to 6.667 ft. Turn it around and a flag of length f suits a pole from 3 x f to 4 x f. A 5 x 8 flag, for example, has a length of 8 ft, so it suits a pole from about 24 to 32 ft tall. The results shown on the page are calculated from your inputs using this rule.

The official US proportion is different. Executive Order 10834, printed with 4 U.S.C. 1, gives the hoist as 1.0 and the fly as 1.9. A US flag 3 ft high is therefore 5.7 ft long. Retail sizes such as 3 x 5 are not exactly that proportion, which is why the tool shows the official figure as a separate result.

Why do the sizing charts disagree, and what does wind change?

The two seller charts do not match each other, and neither matches the rule of thumb exactly. The tool shows each source as typical sizes from the named sources, so you can see where they differ rather than having them merged into one answer.

Guide A lists a single size for each height band. For example, a 20 ft pole has a 3 x 5 flag and a 25 ft pole has a 4 x 6 flag. Guide B gives a range of sizes for many heights. For example, a 20 ft or 25 ft pole has 3 x 5 to 5 x 8. Guide A also says a 20 ft pole suits a flag about 5 to 6.5 ft long.

The 25 ft row shows a clear conflict. Guide A’s 4 x 6 flag is shorter than the rule-of-thumb range for 25 ft, which runs from 6.25 to 8.333 ft, while guide B allows 3 x 5 up to 5 x 8. The tool shows both rather than picking one.

Wind works differently. Guide A advises going one row down in high wind, so with “Windy or exposed site” ticked, a 25 ft pole moves from 4 x 6 to 3 x 5. Guide B says to lower the flag or use a smaller one when the wind is too strong. Guide A adds that a flag larger than advised wears out faster.

Sources (checked 19 October 2026): flagsforgood.com · nationalcapitalflag.com · flymeflag.com · govinfo.gov

Worked examples

Calculated by the tool above; open it with the same values to see each step.

Frequently asked questions

What is the rule of thumb for flag size?

The flag length should be between one quarter and one third of the pole height. For a 20 ft pole, that gives a flag about 5 to 6.667 ft long.

What does hoist x fly mean?

Hoist is the height of the flag, and fly is its length. Both are given in feet, so a 3 x 5 flag is 3 ft high and 5 ft long.

Why does the tool show two sizes for one pole?

Each seller chart uses its own bands, so the two guides do not always give the same size. The tool shows both so you can compare them.

What does the “Windy or exposed site” box change?

With the box ticked, guide A’s answer moves one row down, so a 25 ft pole moves from 4 x 6 to 3 x 5. The “Windy site” result also appears with advice based on the guides.

What is the official US proportion?

It is the flag shape set by Executive Order 10834, with a hoist of 1.0 and a fly of 1.9. A US flag 3 ft high is 5.7 ft long. Enter a height under More options to see it.

Why do I see a warning when I enter a pole height?

Pole heights under 4 ft or over 150 ft show a warning. Blank, zero or non-numeric heights show an error, so check the number you typed.

Related tools

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• Trampoline Sizes: use it to compare sizes when you are planning a yard layout.
• Above Ground Pool Sizes: use it when you need dimensions for a pool in the same outdoor space.
• Landscaping Cost Calculator: use it when you are planning outdoor work around the flagpole.