# RPM Calculator

RPM Calculator

MPH:
Gear Ratio:
Tire Diameter:
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### RPM Formula:

Automatic Without Overdrive = (Gear Ratio x MPH x 355) / Tire Diameter
Automatic With Overdrive = (Gear Ratio x MPH x 336 x .7) / Tire Diameter
Manual = (Gear Ratio x MPH x 336) / Tire Diameter
5 Speed = (Gear Ratio x MPH x 336 x .8) / Tire Diameter

### RPM Definition

Your car doesn’t have a tachometer, or it’s just plain not working. But you need to make sure your car isn’t revving higher than recommended or even lower than it should be. RPM’s are the bread and butter of working an engine efficiently. But you have no idea how to accurately calculate it. Not to worry, we can help with this simple calculator that will help you decide how fast the engine is revving.

### Why Should You Use This Calculator

RPM’s are critical for the life blood of your automobile. If the revs are too high, you run the risk of your engine burning out on the red line. Too low and your engine is liable to stall. And calculations may be entirely too hard to come by. Plus, even assuming you had the calculator and the proper numbers to use, who wants to try plugging in numbers while driving? With texting while driving multiplying your risk of an accident exponentially. In fact, in 2008, it was reported that 16% of all fatal accidents were caused by distracted driving. Using an online calculator from the safety of your house or apartment cuts that out entirely.

### How to Use This Calculator

Just write down the information you want to know the RPM’s for… All you have to do is input the following numbers:

2. Your gear ratio (remember that at different gears, your gear ratio will change)

Then just click the calculate button on our free calculator and the proper RPM’s will appear in just seconds. It’s quick, easy and accurate. You will actually get four numbers for this one:

1. RPM’s for an automatic transmission without overdrive.
2. RPM’s for an automatic transmission with overdrive.
3. A manual transmission.
4. A 5-speed transmission.

### Things to Remember

1. Always write down the numbers you want while the car is stopped or while at home, or have a friend write down the numbers for you. NEVER write down the numbers while the car is in motion.
2. Since your gear ratios can change from gear to gear, and automatic transmissions will change the gear for you. On a manual, you’d be more in control.
3. Most gear ratios are given as a ratio, but you only need the number in front of the 1. For instance, to do a gear ratio of 0.81:1, just type in 0.81.

Getting your best readings with our free online calculator is quick and easy and saves you the trouble of having to pay for costly engine repairs or wondering why the engine keeps stalling. Try our free online calculators today!

### How to Calculate RPM

Let's be honest - sometimes the best rpm calculator is the one that is easy to use and doesn't require us to even know what the rpm formula is in the first place! But if you want to know the exact formula for calculating rpm then please check out the "Formula" box above.