Tell us the number that was wrong

Write to hello@plainnumber.com. It reaches a person, not a queue.

First: the five things it usually turns out to be

Most reports of a “wrong” number are a limit we already know about and state on the page. Checking these first will often get you a faster answer than we can:

• Take-home pay looks too high. It covers federal income tax and FICA only. State and local tax are not included, and in most states that is a large difference. Neither are pension contributions beyond what you entered, health premiums, or wage garnishments.
• The mortgage payment does not match your lender’s quote. Ours is principal and interest, plus whatever tax, insurance and PMI figures you supplied. PMI is estimated at 0.6% where you have not overridden it. Your lender is pricing your actual credit file, and their number is the real one.
• The exchange rate is not what your bank gave you. These are European Central Bank reference rates from a snapshot taken when the site was last built — currently 2026-08-21. They are mid-market rates. Every bank and card adds a margin on top, so the rate you are charged will always be worse.
• The business-day count is off by a day or two. We exclude weekends. We do not know your public holidays, which vary by country, state and employer.
• Cups to grams disagrees with another site. Ingredient densities are approximations and flour in particular varies a great deal with how it was scooped. If you need precision, weigh it.

Every calculator states its own limits next to its answer, for exactly this reason. If one gave you a figure without telling you what it did not account for, that is itself a bug worth reporting.

Reporting a wrong number

If none of the above explains it, please write. The report we can act on fastest contains four things:

• which calculator, ideally the page address;
• the exact figures you entered — we cannot see them, because nothing you type ever reaches us;
• the answer it gave, and the answer you expected;
• where your expected answer came from, if it came from somewhere — a lender’s statement, a payroll stub, a published table.

That last one matters more than it sounds. A disagreement with a figure published by an authority is something we can test against and fix. A disagreement with another calculator usually means the two make different assumptions, and knowing which one you trust tells us which assumption to examine.

Send it to hello@plainnumber.com.

Asking where a figure came from

Tax brackets, the standard deduction, the Social Security wage base and similar published figures link to the authority that issued them, along with the date a person last checked them against that source. If a link is dead, a figure looks stale, or a new tax year has started and we have not caught up, tell us — that is a real bug and it quietly corrupts every answer downstream of it.

The AI disclosure explains how those figures are verified, and why an AI assistant is not permitted to be the reason one appears here.

Suggesting a calculator

Suggestions are welcome and they are the main way this site grows. The useful ones describe the situation rather than the formula: what you were trying to work out, and what you ended up doing instead when you could not find a tool for it.

We are more likely to build something that is genuinely arithmetic and has a defensible right answer. We are unlikely to build anything that needs to know your personal circumstances to be correct, because we cannot know them and would only be guessing on your behalf.

What we cannot help with

• Recovering anything you entered. Not a policy — a fact. The figures never leave your browser, so there is nothing on our side to retrieve. Closing the tab discards them.
• Account problems. There are no accounts, no logins and no subscriptions. If something claiming to be Plain Number asked you to sign in or pay, it was not us.
• Telling you what to do. We can explain what a calculator computed and why. We cannot advise you on whether to take the loan, accept the offer or make the overpayment — see the Terms.

What to expect when you write

This is a small operation, so there is no service-level promise attached to that address and it would be dishonest to invent one. Reports of a wrong number get looked at first, and are the thing most likely to get a same-week fix, because a confidently wrong figure is the only way a site like this really fails. Feature suggestions are read and kept, but may sit for a while.

We will not ask you for personal or financial details in reply. Nobody here needs your account numbers to fix an arithmetic bug, and any message claiming otherwise is not from us.

Privacy of your message

Email is ordinary email: what you send reaches our inbox and is stored there. That is separate from the site itself, which collects nothing — see the Privacy notice. Please do not paste account numbers, card details or anything else sensitive into a support message. To report a calculation bug we only ever need the numbers you typed into the form, which are not secret.