💰 20/4/10 rule calculator: can I afford a Tesla?

So you want to buy a Tesla, but you're wondering if you can actually afford it. Whether you're buying an EV or any other car, using the 20/4/10 rule is a fantastic baseline for vehicle affordability. As Griffin Milks notes, generally speaking there are three main guidelines that people who care about financial literacy try to follow.

This calculator lets you run your own numbers against this framework. You can also compare a strict 4-year loan against a stretched 7-year term to see exactly how much extra interest you'll pay by lowering your monthly payment.

The first step of the rule is putting at least 20% of the car's purchase price as a down payment. Applying EV tax incentives directly to your down payment is a great way to hit that target without draining your cash reserves.

You limit the loan to a 4-year term to lower your total interest paid. If financed over 4 years at a current 1.99% interest rate, you minimize the true cost of ownership.

Many buyers stretch their loan to 7 or 8 years to lower the monthly payment, but that means you'll pay thousands more over the life of the car. As Griffin Milks points out, if Griffin's Garage bumps up that financing to 7 years, then the interest rate bumps up to 5.69%.

You might lower your payment. However, you're paying a total of $8,400 in interest over those 7 years. Only stretch the loan if you can earn a better return investing that money elsewhere.

The final part of the rule states your total monthly car expenses should stay under 10% of your gross income. This includes your loan payment, insurance premiums, and routine maintenance.

As Griffin Milks puts it, keep the total monthly car expenses including your loan payments, insurance, and maintenance below 10% of your gross monthly income. Griffin's Garage highly recommends shopping around for insurance quotes to keep this number as low as possible!