About the Flag Calculator | USA
This tool recommends a U.S. flag size for a given flagpole using two well-established conventions: the flag industry's pole-height sizing rule of thumb, and the U.S. government's official flag proportions.
The formulas
- Pole-height rule of thumb: flag flown on a ground-mounted pole should have a fly (length) of about pole height ÷ 4. A shorter wall-mounted or outrigger pole should use a proportionally larger flag, about pole height ÷ 3.
- Official proportions: per Executive Order 10834 (1959), the U.S. flag's hoist (width) to fly (length) ratio is fixed at 1 : 1.9. Dividing the recommended fly by this ratio gives the matching hoist.
- Nearest standard size: the calculated fly is matched to the closest size on the common retail chart (3x5, 4x6, 5x8, 6x10, 8x12, 10x15, 12x18, 15x25, 20x30, 30x50, 40x60 feet) so you know what to actually shop for.
Practical context
These are conventions, not laws — the U.S. Flag Code does not mandate a specific flag-to-pole ratio, so treat the pole-height rule as a starting point and the 1:1.9 proportion as the one fixed, official figure. If your pole already came with a manufacturer's size recommendation, prefer that over the rule of thumb.
Frequently Asked Questions
How is U.S. flag size related to flagpole height?
A common sizing rule of thumb is that the flag's fly (length) should be about one-fourth the height of a ground-mounted pole, or about one-third the height of a shorter wall-mounted (outrigger) pole. For example, a 20-foot ground pole suits roughly a 5-foot fly.
What is the official proportion of the U.S. flag?
Executive Order 10834 (1959) sets the U.S. flag's official proportions at a hoist (width) to fly (length) ratio of 1 to 1.9. Given a target fly length, dividing by 1.9 gives the matching hoist.
Why do wall-mounted poles use a different ratio than ground poles?
Wall-mounted or outrigger poles are typically much shorter than freestanding ground poles, so a flag sized at one-fourth the pole height would look too small. Retailers commonly use one-third of the pole height instead to keep the flag visually proportionate.
What are standard U.S. flag sizes?
Common retail sizes, given as hoist by fly in feet, include 3x5, 4x6, 5x8, 6x10, 8x12, 10x15, 12x18, 15x25, 20x30, 30x50, and 40x60. This calculator rounds the recommended fly length to the closest of these standard sizes.