Hose Reel Coverage Radius
Calculator

It uses the circle area formula, treating your hose length as the radius from the reel or spigot location, since a hose can reach any point within that radial distance, giving a circular (or partial-circular) coverage zone around the water source.

The calculation assumes a straight line from the spigot to any point, but obstacles like the house itself, trees, fences, or garden beds force the hose to bend around them, effectively shortening the usable reach in those directions below the theoretical straight-line radius.

No, coverage radius depends only on hose length, not diameter; diameter affects water flow rate and pressure at the nozzle, which is a separate consideration from how far the hose physically reaches.

The circle's center simply moves to wherever the spigot or reel is located, so for a spigot in a corner of the yard, much of the theoretical circle falls outside the property, meaning the useful coverage area is smaller than the full circle even though the radius calculation itself doesn't change.

Yes, add extra length for the obstacles and detours mentioned above, plus a few feet of slack for comfortable handling and to reach around corners without stretching the hose to its absolute limit, which stresses fittings and connections over time.