Why Prices Differ Between Methods

Each method looks at your work from a different angle, so they rarely produce the same number. That is by design.

Square inch assumes value scales with area. Bigger pieces are worth more because they take more canvas, more paint, and more wall space. The price grows with size.

Linear inch moderates that curve. It does not penalize small work as much as square inch does, and it does not scale as steeply on large pieces. It is a smoother progression.

Time plus materials ignores size entirely and looks only at your actual investment: hours, materials, overhead, and profit margin. A small piece that took thirty hours will price much higher under time plus materials than under square inch.

When all three converge, the middle of that range is a strong number. It has backing from every angle. That convergence is what you are looking for.

When they diverge significantly, the gap is information. A time plus materials number that is much higher than the size-based methods usually means the piece required more labor than its size suggests. That is real cost the formula is surfacing. Before you dismiss it, ask: did this piece actually take more than usual, and am I accounting for that?

The goal of running all three is not to average them. It is to understand what each one is saying.