How we build and check GlenCalc

GlenCalc has 371 calculators, made by Glenbeam. This page explains where their numbers come from and how we keep them right.

Formulas from published sources

• Each calculator uses a standard formula or a published figure: a tax table, a bag’s stated yield, a building-code limit, a formula from a peer-reviewed study. Every page lists its sources, 197 in all, with the date we last checked the page.
• Where a number varies with the product or the place, such as paint coverage, stone density or a roll’s size, the calculator shows a typical value as an input you can change, and says so. We don’t hide assumptions inside the math.
• The text is written by us. We compare our coverage with other calculator sites only to find topics we’re missing, never to copy them.

Every answer shows its working

Below each answer, the steps that produced it are listed with your own numbers, so you can follow the math, check it, or use it for homework. Most pages also offer a reverse mode for the question asked backwards (“what can I borrow for this payment?”).

Tested before every release

• The worked examples in each page’s questions and answers are recomputed by automated tests, so the text and the calculator can’t drift apart. So are reference results such as tax brackets, statistical critical values and the published examples from official sources.
• Before a release, every page is opened in a real browser at phone and desktop sizes and every calculator is run, checking for errors, layout problems and any request to another site.
• Pages are checked for accessibility and speed with standard tools (axe and Lighthouse).

Figures that change are dated

Figures that change over time live in separate data files, each with its official source, a short quote from that source, the date it was checked and how old it may get. If any figure passes its age limit, the site refuses to build, so a stale number can’t quietly stay live.

• US federal income, payroll, estate and gift tax figures for 2026: checked 2026-10-31.
• Social Security 2026: benefit formula bend points, earnings test and benefit figures: checked 2026-11-02.
• IRS Uniform Lifetime Table (Publication 590-B, Table III) and RMD starting ages: checked 2026-10-31.
• US seller and payment platform fees: checked 2026-10-31.
• US CPI-U, all items, US city average (1982–84 = 100): refreshed automatically from the source each time the site is built.
• ECB euro foreign exchange reference rates: refreshed automatically from the source each time the site is built.

An automated review compares these figures with their official sources every month, and every week from October to January when the IRS publishes next year’s tax figures. It proposes updates with the source’s own wording; a person reviews each change before it goes live. The same review checks that every cited link still works. The full list is on the data sources page.

Limits

The answers are estimates. They are not financial, tax, medical, engineering or legal advice. Tax and benefit calculators use the main federal rules and leave out many special cases. Health calculators use published formulas that describe groups of people, not you in particular. For materials, check quantities with your supplier and follow the manufacturer’s instructions and your local code.

Privacy

Calculations run in your browser and nothing you type is sent to us. Visits are counted anonymously, without cookies. See the privacy notice.

Found a mistake?

Email hello@glenbeam.com with the page and the numbers you used. We fix confirmed errors quickly and update the page’s checked date.