Terms of use

Nothing on this site is professional financial, investment, medical, legal, tax or engineering advice. The calculators produce estimates from the figures you supply, using published formulas that are documented on each page.

Consequential decisions — taking a mortgage, changing your diet, pricing a business, setting a deadline in a contract — should be made with a qualified professional who knows your circumstances. A calculator does not know your circumstances.

We take accuracy seriously: formulas are cited, results are tested against independently derived values, and every calculator states its assumptions and limits. See how we calculate.

We nevertheless make no warranty that any result is free of error or fit for a particular purpose. Formulas are simplifications, rates and thresholds change, and software has bugs. Verify anything that matters.

If you find an error, please report it.

You may use this site freely for personal, educational and commercial purposes. You may not:

• attempt to disrupt, overload or gain unauthorised access to the site or its infrastructure;
• scrape the site at a rate that degrades it for other users;
• republish substantial portions of the explanatory content as your own;
• present results from this site as professional advice you are qualified to give.

To the fullest extent permitted by law, we are not liable for any loss arising from use of this site or reliance on its results, including financial loss, lost profits, or consequential damages.

Nothing in these terms excludes liability that cannot lawfully be excluded, including liability for death or personal injury caused by negligence, or for fraud.

The site is provided as-is and as-available. We do not guarantee uninterrupted access, and we may add, change or remove calculators at any time. Where a calculator is removed, we will keep its URL working with a redirect where a suitable replacement exists.

The explanatory content, design and source code of this site belong to us. The underlying mathematical formulas do not — they are standard, published, and in the public domain, which is precisely why we show them rather than treating them as a trade secret.

You are welcome to link to any calculator. Shared calculation links are designed for exactly that.

These terms may change. Material changes will be reflected in the “last updated” date above. Continued use after a change constitutes acceptance of the revised terms.

Questions about these terms can be sent through the contact page.