Calculate Tire Diameter

Width (i.e. 245):

Height (i.e. 60):

Rim Diameter (in):

Tire Diameter (in) =

Tire Circumference (in) =


Speedo Driven Gear Teeth

Drive Gear Teeth:

Rear Gear Ratio:

Tire Height:

Driven Gear Teeth:

Distance in 1st Gear Calculator

When choosing gear ratios for your transmission and/or rear end, it’s very important to get a good 1st gear ratio.  In fact, I believe it’s a bit more important than the final gear ratio.   

Your Starting Line Ratio (SLR) is a great place to start, but it only reflects part of the info you need to decide on gear ratios.   For example, I have a 4.33 rear gear with a 2.87 1st gear, which is a 12.4 SLR.  That will seem pretty steep to most, but my 31” tires really tame that down to a usable ratio.  So, “by how much” you might ask?   Until I was able to build this calculator, I couldn’t tell you with hard numbers.

First Gear Ratio:

Rear End Gear Ratio:

*Engine Torque:

Tire Diameter (inches):

**Shift RPM:

Total Car Weight:

Approx Distance Travelled in 1st gear (in feet):

This calculator is intended to give you a reasonable approximation of how far your car will travel until you need to shift into 2nd gear.

Yes, there are many variables that will affect this calculation, and ‘no’ this calculator doesn’t attempt to incorporate all possible factors.  For example, these calculations assume zero clutch and/or tire slippage.  And it assumes a linear rate of acceleration, which isn’t necessarily ‘real world’ in most cases.

However, this calculator should provide you with the ability to get an idea of how far you can expect to travel in 1st gear.  And give you a chance to see how various gear ratios will affect your 1st gear usage.  Just bear in mind these calculations give you the MINIMUM distance given the critieria.  You can always extend the distance by letting off the accelerator while driving.

Please feel free to give us some feedback and/or suggestions.  Email Us.

*Engine Torque:  approx. torque of your engine.   Accuracy is not drastically important, just get it close.  Also, try to consider what your engine is putting out for a ‘normal’ acceleration (i.e. from a stop light).   It won’t be putting out a peak torque # unless you have it floored.   If you’re driving a street car, take your best guess.  I chose to use 1/2 of my peak torque for street driving calculations.

**Shift RPM:  At what RPM do you want to shift at?  Consider a full-throttle run, and a ‘normal’ take-off from a stop, at which you would shift more like 2500 RPM.  On a street car, the latter is important to represent everyday driving.

Special thanks to the guys at the F-body Classic mailing list for providing us with the calculations!


Graph for


MPH/KPH (up to 140/225)

Gear Ratios

Here’s some calculations you can use to help determine how a new transmission will affect your overall gearing.

Tire Dia (in):

Gear Ratio:




Show as    MPH   KPH


Compare these transmissions!

 Build Your Own

 TKO-600 5sp (0.64 5th)

 TKO-600R 5sp (0.82 5th)

 3550/TKO II 5sp (0.83 5th)

 3550/TKO/500 5sp (0.68 5th)

 LT1/LS1/Viper T56 6sp

 Aftermarket T56 6sp

 Muncie M20 Wide Ratio 4sp

 Muncie M21 Close Ratio 4sp

 3rd Gen Camaro T-5 5sp

Specify Your Ratios: