PARTS MATRIX CALCULATOR

Margin, not markup

The two words get used interchangeably and they are not the same number. A 50% markup is a 1.5× multiplier and a 33% margin. A 50% margin is a 2× multiplier. Matrices are written in margin because margin is what shows up on the profit-and-loss statement.

sell = cost ÷ (1 − GP%) · multiplier = 1 ÷ (1 − GP%)

The multiplier column in the sheet is there so you can sanity-check a tier against what you already do by feel. If a tier reads 4.00× you are asking for a 75% margin on that band.

The shape of a working matrix

Seven tiers is typical: aggressive on hardware and consumables, moderate through the $75–$400 band where most brake and suspension parts live, and thin on the big-ticket electronics and assemblies where the customer can price-shop the part number in thirty seconds. The default in the sheet is that shape.

The band that decides whether you hit target is $75–$400, because that is where the volume is. Getting it wrong by five points costs more than anything you do at either extreme.

What a matrix is not for

A matrix prices your parts consistently. It does not justify charging OEM money for an aftermarket part, and it does not survive contact with a customer who reads the part number off the box. If a customer asks what you paid, the answer is that you sell parts with a warranty and a technician behind them — see OEM vs aftermarket for where the difference is real.

Wiring it into the estimate

The estimate calculator takes a single GP target rather than the whole matrix, so use the tier that the job’s biggest part falls into. Most shop management systems will hold the full table — the software comparison covers which ones apply it automatically at estimate time.