ETS2 & ATS Gear Ratio Calculator – Speed, RPM and Axle Ratio

Which axle ratio is best for your truck in Euro Truck Simulator 2 or American Truck Simulator? A low ratio gives you a calm engine on the highway, while a high ratio gives you more pulling power on hills. This free gear ratio calculator shows your speed at any engine RPM, and the RPM you need for your cruising speed, so you can choose the right transmission before you spend your money.

What Does This Tool Do?

The ETS2 & ATS Gear Ratio Speed Calculator uses your transmission, axle and tire values to show:

• Tire diameter: calculated from the tire size, for example 315/80 R22.5.
• Speed at a chosen RPM: how fast the truck goes in km/h and mph at that engine speed.
• RPM for a target speed: how high the engine turns at your cruising speed, for example 90 km/h.
• Speed table: speeds from 800 to 2,200 RPM, so you can see the whole range at a glance.

Results update instantly while you type. Everything runs in your browser, so nothing is uploaded and nothing needs to be installed.

What Do the Fields Mean?

• Gear ratio: the ratio of the gear you want to check. For top gear this is usually 1.00 (direct drive), or a value below 1 such as 0.78 for an overdrive gearbox.
• Axle (differential) ratio: the ratio of the rear axle, for example 2.85. You can usually see it in the transmission name when you upgrade your truck.
• Tire size: width in mm, aspect ratio in percent and rim size in inches. 315/80 R22.5 means width 315, aspect ratio 80 and rim 22.5.
• Engine RPM: the engine speed you want to check.
• Target speed: the speed you usually drive at.

How to Use the Calculator

1. Enter the gear ratio of the gear you want to check. Leave it at 1.00 for a typical top gear.
2. Enter the axle ratio of your transmission.
3. Enter your tire size, or keep the common truck size 315/80 R22.5.
4. Enter an engine RPM to see the speed at that RPM.
5. Enter your target speed to see the RPM you need.
6. Compare different axle ratios by changing the value and watching the results and the table.

Low or High Axle Ratio: Which Is Better?

• Low ratio (for example 2.47–2.85): lower RPM at highway speed, quieter engine and lower fuel consumption. Best for flat roads and light or average cargo.
• High ratio (for example 3.08 and above): higher RPM at the same speed, but more pulling power. Best for heavy cargo, mountains and heavy haul jobs.

Tip: Most truck engines work most efficiently in the lower middle of their RPM range. Try to choose a ratio that keeps your cruising RPM in that area.

Frequently Asked Questions

How is the speed calculated?

The formula is: speed = RPM × tire circumference ÷ (gear ratio × axle ratio). The tool calculates the tire circumference from your tire size.

Why is the speed in the game a little different?

The real tire size changes slightly under load, and the game may round some values. The result is very close, but small differences are normal.

Does this work for modded trucks and transmissions?

Yes. Enter the ratios from the mod's description and the calculation works the same way.

Is this tool free?

Yes. It is completely free and works on desktop and mobile.