Calculating How Much Paint You’ll Need to Paint Your Vehicle

One of the most common questions that comes up when planning to paint a car is “How much paint will I actually need?” It’s a great question for a lot of reasons, not least of which is knowing how to budget. And while no one wants to buy more material than necessary, you also want to make sure you have enough to get through the job in one shot.

There is no single formula for calculating how much paint you’ll use. Instead, the answer will come down to several factors. Clearly the size of the vehicle (and how much of it you’ll be painting) is one of the most critical inputs. But the type of paint – single stage, basecoat, or clear, for instance – will also factor heavily, as will your personal experience as a painter.

Here is a primer (no pun intended) on how to calculate how much material you’ll need to paint your project based on these factors. The formula will be:

(A [Surface Area] + O [Overage] x N [Number of coats]) / C (Coverage) = V (Volume in gallons)

Factors

Surface area – Most paints will include the total coverage of the product in terms of square feet. This may range from around 100 square feet per gallon to three or four times that, depending on the paint chemistry. Regardless of the actual number, this will be an estimation to apply a single coat of catalyzed paint.

Calculating the exact surface area to painted can be tricky, but you can get a close number by measuring the vehicle in large rectangular blocks, rounding up to the nearest foot for simplicity. You’ll need to measure the areas of each of the major “blocks” to be painted and add them up to get a total. We’ll use our Chevy C-10 project truck as an example below, calculating only for painting the exterior panels, except for inside the bed.

Bedsides (left and right): 9’ x 3’ = 27 sq ft x 2 sides = 54 sq ft

Lower cab & front fenders (left and right): 9’ x 3’ = 27 sq ft x 2 sides = 54 sq ft

Hood: 6’ x 5’ = 30 sq ft

Roof: 6’ x 3’ = 18 sq ft

Cab back (including cab pillars): 6’ x 5’ = 30 sq ft

Tailgate (inside and outside): 6’ x 2’ = 12 sq ft x 2 sides = 24 sq ft

Total area = 54 + 54 + 30 + 18 + 30 + 24 = 210 total sq ft of surface to be painted. This total must be multiplied by the number of coats for the product (base, clear, etc.) you’ll apply to get a material total for each one.

Overage factor – Even though you’ve rounded up you measurements, you’ll still want to factor in a little extra material in case you have a spill, make a mistake that needs to be reshot, or want to hold a little bit in reserve for touchup later. The amount you factor in will be your call, but many painters prefer to mix between 10% (0.1) and 20% (0.2) additional material for each sprayout, so you’ll want to factor similarly for your total overage. For our formula we will add the overage in decimal form to the number “1” to get the factor (i.e., 1.2 for a 20% overage). Most likely, you’ll round up to the nearest gallon when painting an entire vehicle.

Paint coverage – Different paints have different coverage rates. Some single-stage paints tend to lay down a little heavier than similar base/clear colors, for instance. In the case of GM Rally Red, Eastwood’s 3:1 single-stage paint covers approximately 125 sq ft per gallon, while the same color in the 4:1 base/clear system is good for about 160 sq ft per gallon. Eastwood’s clearcoats fall in between, with the 2:1 European Urethane Clear covering ~150 sq ft per gallon and the 4:1 Premium Show Clear laying down about 140 sq ft.

Carefully read each product’s label or instructions to find its specific coverage, and keep in mind this number represents an estimate for a single coat of fully catalyzed paint. Actual coverage can still vary based on the paint gun being used, air pressure going to the gun, ambient temperature and other factors at the time it’s sprayed.

Number of coats  – How many coats of each product you spray will be the final calculation. Typically, you’ll want to factor two to three coats of color (single-stage or base/clear) and three or more coats of clear for a quality show finish, allowing for minor nibbing and scuffing as needed between coats. The actual number will be dependent on your priorities, time, and budget.

For reference, the owner of this 1968 Dodge Charger used three gallons of Chrysler’s Plum Crazy Purple and five gallons of clear on his home-sprayed project, covering virtually every piece of bodywork in a deep, smooth shine.

Doing the math

Using the measurements from the C-10 above, let’s calculate the how much paint would be required to spray two coats of Eastwood’s ready-to-spray OEM Select basecoat in its current Porsche Signal Green (@300 sf/gal) and three coats of 2:1 European Clear, factoring for a 20% overage. The formula will be:

(A [Area] + O [Overage] x N [Number of coats]) / C (Coverage) = V (Volume in gallons)

Sample results

Paint – (210 x 1.2 x 2)/300 = 1.68 gallons

Clear – (210 x 1.2 x 3)/150 = 5.04 gallons