Flag Size for Pole Height Calculator
Enter your flagpole’s height and get a recommended flag size — the fly, the matching hoist, and the closest common off-the-shelf size.
Recommended flag size
How the recommendation is calculated
The calculator multiplies your pole height by 0.25 for the recommended fly length, and reports the full acceptable band from 0.25× up to 0.33× (one-third) of the pole height. The hoist then follows from your chosen ratio: hoist = fly × (ratio’s hoist number / ratio’s fly number).
A taller pole simply scales every figure up proportionally — a 40-foot pole calls for roughly double the flag of a 20-foot pole, all else equal.
Frequently Asked Questions
Where does the "quarter of the pole" rule come from?
It's a long-standing rule of thumb among flag manufacturers and flagpole installers: a flag's fly (its horizontal length) should run roughly one-quarter to one-third of the pole's height. Much smaller and the flag reads as an afterthought on a tall pole; much larger and it puts excess strain on the halyard, snap hooks, and pole hardware in wind.
Why is there a range instead of one exact number?
Site conditions vary — a windy coastal location favors the smaller end of the range to reduce wear, while a sheltered spot can carry the larger end for better visibility. The calculator reports the full quarter-to-third band along with a recommended midpoint so you can adjust for your own setting.
How do I get the vertical (hoist) dimension?
Once the fly is set, the hoist follows from your flag's ratio — a 2:3 flag's hoist is two-thirds of its fly, a 1:2 flag's hoist is half its fly, and so on. Pick the ratio that matches the flag you're flying and the calculator scales the hoist to match.
What if my pole height falls between standard flag sizes?
Off-the-shelf flags come in a limited set of sizes, so the calculator also reports the closest common fly length to your recommended figure. Rounding to the nearest standard size is normal practice and keeps replacement flags easy to source later.
Educational tool only. This is a common sizing guideline, not a building code or manufacturer specification — check your flagpole's own documentation and local wind conditions before ordering.