About AxleMath
Three years over the road taught me which numbers actually matter out here. AxleMath is those numbers, done right, without the app store.
By Avery Schwartz — former CDL-A driver, 3 years OTR.
I learned scale math the way most drivers do: sitting in a CAT scale parking lot with a ticket that said my drives were 1,100 pounds over, doing hole arithmetic on the back of a fuel receipt while a reefer idled behind me waiting for the platform. The apps that promised to help were download-only, buried the answer under ads, or — worse — got the direction wrong. Everything else that mattered was the same story: cost per mile lived in a spreadsheet I built in a Walmart parking lot, per diem was a rumor drivers argued about on the CB, and recap hours were something you counted on your fingers at midnight.
When I came off the road, I built the tools I kept wishing existed. Every calculator on this site:
- Works in the browser — nothing to install, loads on truck-stop wifi.
- Answers like a driver needs — "slide 5 holes forward," not a wall of decimals.
- Shows its work — the formula, the assumptions, and two worked examples sit under every tool.
- Stays free — supported by ads, never by locking the answer behind a signup.
The results print out like the scale ticket in your hand because that's the format the answer has to match. Start with the tandem slide calculator — it's the tool the whole site was built around — or the guides if you want the longer version of how any of this works.
Why accuracy is the whole point
A wrong calculator out here isn't an inconvenience — it's a citation, a blown tax deduction, or a truck note you can't carry. So the math on this site tracks the actual sources: the federal bridge formula as written in 23 CFR 658.17, hours of service per FMCSA Part 395, the IRS special transportation-industry per diem rates, and loan amortization the way a lender actually computes it. Where the real world varies — trailers slide differently, states write their own bridge laws, rates change — the tools say so instead of pretending.
The fine print
Everything here is an estimate. Verify axle weights at a certified scale, confirm hours against your ELD, and run tax questions past a professional before filing. If a calculator ever gives you a number that doesn't match the reweigh, I want to know about it.
Contact
Questions, corrections, or a tool you wish existed: send it through the contact page. Every message gets read.