Even though not all driver’s exams require you to parallel park, sometimes real life does. For those times where you can’t call the AAA helpline, below is the mathematically accurate way to parallel park without a scratch.

The instructions are based on a formula [PDF] created by Simon R. Blackburn, a mathematician at Royal Holloway, University of London. He used the Pythagorean Theorem and a series of variables (the radius of the car’s turning circle, the distance between front and back wheels, the distance from the center of the front wheel to the front of the car, and the width of the already-parked car) to devise what he calls a “perfect parking” maneuver, in which the car swings directly into the empty spot with no additional wiggling required. If you plug values specific to your situation into the formula, it’ll tell you how long the parking space needs to be in order for you to parallel park perfectly.

As you’re probably thinking, it’s unlikely that you’ll be able to whip out your pocket yardstick and start measuring distances on the fly. So Men’s Health translated the math into four easy-to-follow steps:

1. Pull alongside the car ahead of the spot you want and align your rear tires with that car’s bumper.
2. Turn your wheel toward the curb as far as it will go.
3. Back up until the center of your inside rear tire aligns with the street side edge of that forward car. Straighten the wheel and keep backing up.
4. When your outside tire aligns with that same edge, turn your wheel out toward the street and keep reversing.

Hypothetically, your car should slide right into the spot and you can christen yourself a certifiable master of parallel parking. Having said that, a little wiggling never hurt anybody, and you can still consider your car successfully parked even if it takes you a few extra maneuvers.

And don't forget to check out these 15 other hacks to make your parking experience as perfect as possible, parallel or not.

[h/t Men’s Health]