How Numberwright makes and checks its numbers

Numberwright calculators are fixed formulas written down from published sources. Nothing here is a guess, and none of the settings or limits are numbers we made up.

From source to formula

For each calculator we start from a primary source: a university extension publication (Mississippi State, Clemson), or a government agency (USDA). We write the formula in plain words on the calculator's page, then in code. The Sources page lists everything we used.

How we test

Every formula runs in automated tests before a release. Where a source publishes a worked example, the test uses it: the Mississippi State and USDA NRCS examples for lime and pure live seed; the Mississippi State fertilizer example; and Clemson's spreader-calibration example.

What we do not do

We do not use AI to produce results: every number comes from a fixed formula. We do not store what you type. We do not give legal, medical, food-safety or professional advice: the calculators help you check your numbers against the rules, manuals and labels that apply to you, and those always come first.

Keeping numbers current

We re-open every source every three months. When a rule or value changes, we change the formula, the tests and the page, and update the "Last reviewed" date. A real mistake is recorded on the Corrections page.

How this site was made

Numberwright is built and maintained by an independent developer, using AI assistance to draft code and text. Results are never generated by AI: every number comes from a fixed formula, written from the published sources listed on the Sources page and tested against the worked examples those sources publish, where they publish one. If you find a mistake, please tell us.

Last reviewed: 27 Oct 2026