Corrections policy

Calculators can be wrong. A formula can be misapplied, an edge case can be missed, or a figure taken from an outside source can go out of date. This page explains how to report a problem and what happens next.

Reporting a problem

Email hello@numvella.com. The report is much easier to act on if it includes:

A link to the calculator or page.
The exact values you entered.
The result you got, and the result you expected.
Where your expected figure comes from, if it is from a specific source or method.

Calculations run entirely in your browser, so we have no record of what you entered. If you do not include your inputs, we usually cannot reproduce the problem.

How a report is investigated

Reproduce it. We run your inputs through the same calculation function the page uses. If we cannot reproduce the result, we come back to you rather than closing it.
Separate the two possible faults. Either the code does not implement the formula correctly, or the formula is not the right one for the case you describe. These need different fixes, and the second sometimes means the page needs to explain a limitation rather than change a number.
Write a failing test first. A confirmed calculation error gets a test that reproduces it and fails. That test then has to pass, and it stays in the suite so the same error cannot return unnoticed.
Fix and verify. The fix ships with the full test suite passing. See Methodology for what the suite does and does not cover.

What happens to the page

If a calculation changes, the page's formula, examples, and any affected explanation are updated to match — an example that no longer reflects what the tool outputs is itself an error. If the problem was that a limitation was not explained, we add the explanation instead of changing the maths.

Where a fix materially changes a published result, we say so on the page rather than editing it silently.

Dates

A review date is only added or changed when a review actually took place. We do not update dates to signal freshness, and an unchanged date means the page has not needed a review — not that it has been forgotten.

What we cannot help with

We cannot tell you which figure to use for your own financial, medical, tax, or legal situation, or confirm that a result is appropriate for a decision you are about to make. Those questions need a qualified professional who knows your circumstances. What we can do is make sure the arithmetic on this site is right and that its assumptions are stated plainly.

Reporting something other than a calculation error

Broken links, accessibility problems, unclear explanations, and missing edge cases are all worth reporting to the same address. See Contact.