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If a calculator returns a figure you believe is wrong, or cites a source that no longer says what we attributed to it, please tell us. Include the page URL, the inputs you used, and the result you expected. If you have the authoritative source to hand, send that too — it is the fastest route to a fix.

Published figures go stale in ways no automated check catches. Tax rates are revised mid-year, governing bodies amend formulas between seasons, standards are superseded. A correction from someone who works with the numbers daily is worth more than another round of our own review.

If there is a calculation you keep doing by hand, tell us what it is and, if you know it, where the formula is published. We build from primary sources, so a pointer to the governing body's own documentation makes a request far more likely to be built.

For help with sign-in, saved calculations, or deleting your account and its data, use the same address and mention the email your account uses.

Calculators marked as embeddable may be embedded with attribution. For licensing, bulk use, or anything else commercial, get in touch and describe what you have in mind.

We cannot give financial, medical, legal or veterinary advice, and we cannot tell you what to do in your particular situation. Our calculators show a formula and a result; interpreting either against your circumstances is a conversation to have with a qualified professional.

For a medical emergency contact your local emergency service. For a suspected poisoning in a pet in the United States, contact the ASPCA Animal Poison Control Center on (888) 426-4435 or your veterinarian immediately — do not wait on an email from us.