How we build a calculator
- Choose the formula from a named source. We start from a primary source, such as an industry methodology, a standards body or a well-established reference, not from another calculator site.
- Show the math. Each page shows the formula, defines every term and says what is included and what is left out.
- Work an example by hand. We calculate the example on the page by hand and confirm the calculator gives the same answer.
- Source every benchmark. A range such as “a healthy ratio” always names where it comes from, so you can judge it yourself.
- Check before publishing. A person reads and checks the page against its sources before it goes live.
- Date the check. The “last checked” date on a page changes only when we have actually checked the formula and sources again.
What the results are
Results are estimates based on the numbers you enter and the formula shown. Your own accounting rules, definitions and circumstances may differ, so use a result as a starting point for a decision, not as the decision itself. Calculators are not tax, legal or financial advice.
When definitions differ
Some metrics have more than one accepted definition. Where that is the case, the page says which one we use and why, so you can compare like with like.
Corrections
If you think a formula, number or source is wrong, email hello@webtilly.com. We check it, fix it if needed and update the date on the page. How we handle changes is covered in our editorial policy.