Square footage is the starting point, not the whole story
National cost guides list a home's size and shape, the siding material chosen, removal fees, and labor costs as the main drivers of a siding bill, and specifically call out that the number of stories affects labor on its own.[1]
Two houses with identical wall square footage can land on noticeably different bids once one of them is a story taller than the other.
Why a second story costs more than its share of the wall
Working above the first story requires scaffolding, staging, or a lift, plus more time moving material up and down, none of which shows up in a simple square-footage number.
A single-story ranch and a two-story colonial with the same total wall area rarely price the same, because the ranch crew never leaves the ground.
Roofline and wall complexity
A rectangular footprint with few corners lets a crew move fast and waste little material, while dormers, bay windows, and multiple roof pitches slow the same square footage down considerably.
Every inside or outside corner needs its own trim piece cut and fitted, which adds labor time that a flat per-square-foot number doesn't capture on its own.
Why your metro's labor rate is the other half of the equation
Carpenters nationally earned a median wage of $29.12 an hour as of the most recent BLS estimate, but that figure moves considerably by metro, and this site's calculator adjusts for your own metro's rate rather than showing a flat national labor cost.[2]
Since labor commonly runs 30% to 50% of a siding bill, a metro with wages well above the national median pushes the whole estimate up even before the material choice is factored in.[3]
Site conditions that have nothing to do with the wall itself
A house set close to a property line or behind a locked gate can slow material staging and add labor time that has nothing to do with the siding itself.
Mature shrubs or a deck built up against the foundation often need to be temporarily moved or protected during the job, and some bids price that separately while others fold it into a general site-condition line.
Reconciling two bids that measured the house differently
Two bids quoting noticeably different wall-area totals for the identical house usually means one of them measured wrong, not that one contractor is simply cheaper.
Reconciling the measured square footage between bidders first, before comparing their dollar figures, is the clearest way to tell whether a price gap traces back to labor rates or to a plain measurement error.
What to do with all of this before requesting a bid
Use this calculator's wall-area estimate as a baseline, then expect a bid on a taller or more complex house to run above that baseline even at the same square footage.
Asking two contractors to bid the identical scope, on the identical measured wall area, is the only way to isolate their labor rate from all the other variables covered here.
A bid that's silent on stories, roofline complexity, or site access isn't necessarily wrong, but it's worth asking the contractor to confirm they actually priced those factors rather than quoting off a flat square-footage rule of thumb.