Editorial and calculation methodology

How we choose a formula

We only build calculators for calculations that have a single, settled definition - gross profit, food cost percentage, VAT, break-even, contribution, yield. Where a term is used loosely in the trade (markup versus margin is the classic example), we state which definition the calculator uses on the page itself and show the arithmetic rather than hiding it.

Where a figure is set by law or by HMRC - VAT rates, National Minimum Wage, employer National Insurance, pension contributions, holiday entitlement - we do not restate the number as though it were ours. We link to the relevant GOV.UK page and let you enter the rate that applies to your business.

How calculators are tested

Each calculator is checked against a worked example computed independently of the code. The worked example published on every calculator page is the same test: if the numbers on the page do not reproduce in the tool, the tool is wrong and we fix it. Edge cases - zero inputs, negative margins, division by zero, non-standard VAT rates - are checked before a calculator is published.

How we choose sources

We cite primary sources only: GOV.UK and HMRC for tax, pay and employment rules. We do not cite blog posts, aggregator sites or unattributed "industry averages". Where a source is cited, the link goes directly to the page that supports the specific claim.

We deliberately do not publish benchmark figures such as "the average restaurant runs a 68% GP". We have no verified dataset behind numbers like that, so we do not print them. Any percentage you see in a worked example is an illustrative figure inside that example, not a benchmark you should target.

How often content is reviewed

Every calculator page carries a "last reviewed" date. Pages that depend on rates set by government - VAT, wages, National Insurance - are reviewed at least annually and after any Budget or Autumn Statement that changes a rate we reference. Pages built purely on arithmetic are reviewed annually. We update the reviewed date only when the content has actually been checked or changed; we do not refresh dates to make pages look newer.

Use of AI assistance

Some drafting and all of our article translations are produced with AI assistance. AI output is never published unchecked: formulas, arithmetic and any factual claim are verified by a person before the page goes live, and translated articles are only published for languages where the translation is complete and readable. Where a translation is incomplete or of insufficient quality, the page is excluded from search indexing until it is fixed.

Human review

Dumb Bambi is an independently run site. Calculations, worked examples and page content are reviewed by the site owner before publication. We do not attribute content to named experts, reviewers or qualifications, because we will not publish credentials we cannot evidence.

Articles are published under a single byline, the Dumb Bambi Editorial Team. Technology may assist with drafting and translation, but calculations, examples and published information are checked before publication.

Corrections policy

If a calculator returns a result you believe is wrong, or a page contains an out-of-date rate, tell us and we will check it. Send the calculator name, the figures you entered and the result you expected via our contact page. Confirmed errors in a calculation are corrected as a priority, and the page's reviewed date is updated when the fix is published.

How the site is funded

The calculators are free to use and are funded by advertising and by partnerships with hospitality suppliers. Advertising never influences a formula, a worked example or a recommendation. Ads are labelled and kept separate from calculator controls, and advertising cookies only load if you have accepted them in our cookie settings.

Limitations and disclaimer

Our calculators are decision-support tools for general business use. They are not accounting, tax, legal or financial advice, and they cannot account for the specifics of your business, your VAT position or your contracts. Results depend entirely on the figures you enter. Before you act on a result - filing a return, changing prices, restructuring a rota - check it against your own records and, where the stakes justify it, with your accountant or adviser. Full terms are in our terms and conditions and disclaimer.