This page explains where our formulas come from and how each calculator gets checked before it’s published. It exists so you don’t have to take a result on faith.
Where the Formulas Come From
Every calculator on CarsMath is built from one of three sources:
- Manufacturer specifications — published figures from vehicle, engine, or parts manufacturers.
- SAE or EPA references — standards such as SAE net horsepower correction (SAE J1349) or EPA fuel economy test procedures.
- Established tuning sources — formulas that are widely used and documented across the automotive tuning and performance community, not a single unverified forum post.
We don’t code a formula from memory and publish it. If a formula can’t be traced to one of the sources above, it doesn’t go live.
How a Calculator Gets Built
- The underlying formula is identified and matched to a source.
- The formula is tested against known reference examples, where they exist, to confirm it produces the expected result.
- The calculator page states the formula in plain view, so you can check the math yourself.
- Units and edge cases (zero values, negative inputs, unrealistic ranges) are checked before publishing.
How We Handle Updates
Standards change. When SAE, EPA, or a manufacturer revises a figure or a method, the calculator that relies on it gets updated to match. Older calculators are reviewed on the same basis as new ones — publish date isn’t a reason to skip a recheck.
When a page is meaningfully updated, we note the change rather than silently swapping numbers.
What Our Calculators Are — and Aren’t
CarsMath calculators give estimates based on standard formulas and the numbers you enter. They’re a starting point for understanding a spec or a cost, not a replacement for a manufacturer’s official rating, a dyno run, a mechanic’s inspection, or a dealership quote. Real-world results vary with conditions, wear, and individual vehicles.
Report an Error
If you find a formula that looks wrong, or a source that’s out of date, tell us through the Contact page. We check every report against the original source before making a change, and we’d rather fix a real error than defend a mistake.