Shop & Body Calculators

Shop and body work is mostly about quantities and budgets: how much paint, primer or filler to buy, what size of wire to run, how much to budget for a restoration, and how to keep the shop warm and clean. The tools here turn areas and coats into amounts and add an allowance for waste.

Which tool answers which question

• Auto paint calculator: How much paint, hardener and reducer to buy for single-stage or base coat and clear coat. Every default is editable, because your product's tech sheet...
• Body filler and primer calculator: How much filler to mix for the areas you're repairing, and how much primer to buy for the film build you want. The primer math uses the same physics paint...
• Brake pedal ratio and line pressure calculator: Pedal ratio, the force reaching the master cylinder, and the line pressure it makes. Handy when swapping to manual brakes, changing master cylinders or...
• EV vs Hybrid vs Gas Cost to Operate Calculator: Compare estimated annual fuel or energy cost across a gas vehicle, hybrid, and EV.
• Powder coating calculator: How far a pound of powder goes and how much you need for a part, from the powder's specific gravity and the film thickness you're after.
• Pressure Washer Chemical Dilution Calculator: Work out how much chemical to add to hit a target dilution ratio for your tank size.
• Restoration budget planner: Lay out the whole project by area with your own numbers, plus a cushion for surprises. Copy the link to save your budget or share it.
• Sandblaster compressor CFM calculator: How much air your blasting nozzle uses, so you can tell whether your compressor can keep up. Nozzles wear bigger with use, so it also shows the demand once...
• Automotive wire gauge calculator: The smallest wire that keeps voltage drop in check for a 12-volt circuit, based on how much current it carries and how far it runs.
• Workshop Heating (BTU) Calculator: Size a garage or workshop heater based on your space, insulation, and climate.

Paint, primer, filler and powder coat

Paint and primer quantities depend on the surface area, the number of coats, the product's coverage and how much it is thinned or reduced. The tools add an allowance for overspray and waste, and the product's technical data sheet has the exact mixing and coverage. Prep decides the result, so primer and filler quantities are worth planning as carefully as the paint. Painting, priming and powder coating all need ventilation and the protective gear the product specifies.

Wiring, brakes and budgets

Wire gauge depends on the current and the length of the run, because longer runs lose more voltage. Use a gauge rated for the load and protect circuits with a properly sized fuse. A brake pedal ratio changes pedal effort and travel and does not replace a brake inspection. Restoration and engine budgets are planning aids, and real costs tend to run over, so keep a reserve.

Common mistakes

• Buying paint without checking coverage. Use the technical data sheet.
• Skimping on prep. Filler and primer determine the final finish.
• Using wire that is too small. It overheats and drops voltage.
• Skipping ventilation and respiratory protection. Fumes and dust are the main shop hazard.

Guides for this section

Want the background behind these tools? These guides explain the thinking and the numbers in more depth.

• Planning a Paint Job: Prep, Primer, Base and Clear
• Wiring a Garage: Subpanels, Circuits and Wire Gauge
• Heating and Cooling a Garage Workshop
• Choosing Blasting Media and Preparing Metal for Coating
• All guides