Stop Guessing Your Gear Ratio: Use This Free Quarter Midget Calculator
If you've ever stood in the pits after a practice session staring at a gear chart, doing mental math on a ratio that doesn't seem right, this one's for you.
VAST has teamed up with my-qm.com to offer a free, purpose-built quarter midget gear ratio calculator, and it's genuinely one of the most useful tools you can have on race day. No app download, no subscription, no calculator app math. Just open it in your phone browser, plug in your numbers, and get your answer.
Why Gear Ratio Matters More Than You Think
Quarter midget gear selection isn't the same as swapping sprockets on a go-kart. Your engine has an internal gearbox that multiplies the ratio before the chain is even involved, and that internal ratio changes everything. A one- or two-tooth move on the axle gear has a bigger effect than it looks like on paper, because that change is being multiplied through the gearbox before it hits the rear axle.
Get it right and your driver pulls out of the corners with authority and hits their RPM peak right where the track opens up into the straight. Get it wrong and the car either bogs off the corner or hits rev limiter before the checkered. The difference between a solid top-five and a car that's a step off all night can come down to one tooth.
The math is straightforward once you have a formula, but standing in the pits trying to work it out from scratch on every session is where things go sideways. That's exactly what this calculator solves.
What the Calculator Does
Open my-qm.com on your phone, select your gearbox, enter your current RPM, enter your target RPM, pick your current gears, and hit Calculate. That's it.
What you get back:
- Every gear combination ranked by how close it gets you to your target RPM, with the delta shown for each
- The best match highlighted in green at the top of the results list
- A full gear reference chart (the same style used by engine builders) with your best match highlighted directly on the grid so you can see the full ratio landscape at a glance
The reference chart is especially useful. Most gear charts just show you a static grid. This one updates live when you switch gearboxes, and highlights exactly where your best combination falls on the grid, so you can see what's one tooth away in either direction before you make a decision.
Supported Gearboxes
The calculator supports all three gearbox types used in competitive quarter midget racing:
- Honda (6.14:1 internal ratio): Jr Honda, Sr Honda, Heavy Honda, and all 160cc classes
- Briggs & Stratton (6.07:1): Junior Animal, Senior Animal, Unrestricted Animal, Light/Heavy/Mod World Formula
- Deco (5.73:1): select local and regional classes
Select your gearbox and the internal ratio is applied automatically. You don't need to know the number; the calculator handles it.
Engine sprocket range is 28–38 teeth and axle gear range is 24–34 teeth, which covers the overwhelming majority of competitive NASCAR Youth Series setups.
Save Your Gear Inventory: The Feature That Makes It Track-Ready
The calculator is free to use without an account, and for a quick calculation you don't need one. But creating a free account unlocks the feature that makes it genuinely more useful in the pits: saving the gears you actually own.
Rather than showing you every theoretical combination, the calculator filters results to show only gear combinations you can build right now with the gears in your trailer. If the closest combination to your target requires a 31-tooth axle gear you don't have, the calculator skips it and shows you the next-best option using what you've got.
No more sorting through combinations you can't run.
Saved setups also work as a setup log. Label each saved result with a track name and date, and over the course of a season you'll build a real reference. That's especially useful when you return to a track you haven't visited in a year and want to know where you started last time.
Creating an account is free. Email, password, done.
Add It to Your Home Screen
Since my-qm.com is a mobile web app, you can add it to your home screen so it opens full-screen just like a native app. No address bar, no browser chrome, instant access from the pit lane.
On iPhone (Safari only): Open my-qm.com in Safari → tap the Share button → tap "Add to Home Screen" → tap Add. Done. This doesn't work in Chrome on iPhone, so use Safari.
On Android (Chrome): Open my-qm.com in Chrome → tap the three-dot menu → tap "Add to Home Screen." On many Android phones, Chrome will pop up an "Install app" banner automatically at the bottom of the screen, so just tap that to skip all the steps.
Once it's on your home screen, your login stays active between sessions. Your gear inventory is always ready when you open it.
Tips for Getting the Most Out of It
Get your RPM from real track time. A tachometer or data logger gives you actual current RPM. Estimated numbers produce estimated results, and it's only as accurate as what you put in.
Use the reference chart alongside the results. The grid shows you the full ratio landscape, not just the single best match. See how close neighboring combinations are before you commit to a direction.
Set up your gear inventory before race day. Enter your inventory at home on the couch. At the track, the filter is already working and you're not wasting time.
Make one change at a time. Gear ratio is one variable. Change the gear first, evaluate, then decide whether to combine it with a spring change, hub swap, or weight adjustment. Stack too many changes at once and you lose the ability to know what actually worked.
Get the Gears You Need from VAST
Once the calculator tells you what combination you want, VAST has you covered. We stock quarter midget axle gears in multiple tooth counts, machined for standard quarter midget axle hubs, in #40 pitch chain, ready to ship from Madison Heights, Michigan.
VAST Quarter Midget Axle Gear →
Questions? Give us a call at 248-414-1835, Monday–Friday 9AM–4PM Eastern.