Pick a calculator
Fuel & Fluids
Trip fuel cost, DEF consumption, and coolant mix ratio.
02Gear Ratio & Tires
Engine RPM at speed, and speedometer error from tire size.
03Towing & Payload
Payload capacity and trailer tongue weight.
04Engine Displacement
Bore, stroke, and cylinder count to CID and liters.
05Shop Tools
Torque conversion, Ohm's Law, and battery runtime.
06Trip Planner
ETA, tire pressure vs. temperature, and stopping distance.
07Hours of Service
Remaining drive time under the 11/14-hour rules.
08Axle Weights
Front/rear axle load distribution for a straight truck.
09Cargo & Load Space
Cargo volume and pallet count for a bed or trailer.
10Cost Per Mile
Operating cost per mile and a suggested minimum rate.
11Tire Tread Life
Remaining tire miles from your current wear rate.
Guides
Longer reference reading behind six of the calculators above.
Built for the shop, the field, and the road
Every calculator here uses standard automotive and trucking-industry formulas — the same math a diesel tech, fleet mechanic, or gearhead would use with a notepad. Enter your numbers and get a straight answer: gallons, ratios, pounds, or cubic inches, plus notes on where the formula comes from so you're not trusting a black box.
Results are estimates for planning purposes. Always confirm critical figures — towing capacity, payload, and gearing — against your vehicle or equipment manufacturer's specs before loading or driving.
Who it's for, and how the numbers are checked
PitStopCalc is for people who do this math on the job or in the driveway: owner-operators checking axle weights before the scale, diesel techs and fleet mechanics, farmers moving equipment on a gooseneck, and anyone towing a camper who wants to know which rating runs out first. It's free, there's no account, and it works on a phone in the cab.
Every calculator prints the formula it used next to the answer, so you can redo the arithmetic yourself. Each page also carries a worked example and reference tables, and every table row can be typed into the calculator and reproduced exactly. That rule has caught real mistakes before they were published.
When a number comes from a rule or a standard, the page links to the primary source rather than a summary of it: the federal regulations on eCFR for hours of service, brakes, tires, cargo securement and inspection; the FHWA for truck size and weight limits; and the bodies that publish the standards, such as SAE International, ASTM, API and the U.S. Tire Manufacturers Association. The stopping-distance model, for example, is checked against the FMCSA CDL manual's own figures at 55 mph and comes within 2 feet of its 322-foot total.
In August 2026 all eleven calculators were re-checked against hand calculations, and six errors were found and fixed, including a stopping distance that had been using a passenger car's brakes instead of a loaded truck's. Corrections go out in all six languages at once. If a number looks wrong to you, tell us. The About page describes every check in full.
Common questions
How accurate are these calculators?
Each calculator uses standard formulas and prints the formula it used on the same page, so you can check the arithmetic yourself. They are estimates for planning — the ratings on your vehicle's door placard, the manufacturer's specifications and the rules of your jurisdiction are what actually govern.
Which rating actually limits what I can tow?
Whichever one you reach first. Payload, gross combined weight and axle limits are separate ceilings, and the brochure figure is usually the most generous of them. The towing calculator shows them side by side so you can see which one binds before you load.
Do the hours-of-service figures apply outside the United States?
No. Those limits are the US federal rules for commercial drivers. Other countries set their own, and some US states and exemptions modify them. Treat the result as a rough check against your own logs, never as a compliance record.
Can I work in metric instead of miles and gallons?
Yes. Every calculator has a unit toggle, and switching the site's language switches the default measurement system with it. You can change it back at any point without losing what you have already typed in.
Do I need an account, and what happens to my calculations?
No account, and nothing is uploaded. Anything the site remembers is stored only in your own browser, which also means it does not follow you to another device and clearing your browser data removes it.