Calculators

Reviewed calculator tools, each with a per-page methodology and a source table you can verify against primary sources. Every tool on this page is free, runs in your browser, and requires no account or email address.

The set is deliberately small. Rather than publishing a calculator for every search term, we maintain a focused group covering the money questions that self-employed people, online sellers, and freelancers actually run into: what a marketplace takes from each sale, what the IRS expects during the year, and what an hourly rate is worth once unbilled time is counted. Each one is maintained against its primary source rather than left to go stale.

What every calculator on this page includes

The tool itself is the smallest part. Each page also carries the formula written out in full, the assumptions behind it, a plain statement of what the calculation does not cover, at least one worked example with real dollar figures, a source table naming each figure's origin and the date it was last checked, and a scenario comparison so you can put two situations side by side. A sensitivity view shows which single input moves the result most, and every result can be downloaded as a plain-text summary that includes your inputs, the formula version, and the limitations.

Where a number comes from a published schedule, such as an IRS rate or a marketplace fee, it is cited. Where a number depends on your circumstances, it is an editable input labelled as an assumption. We do not present a guess as a published figure.

How to choose the right one

Selling physical products. Use the Etsy or Amazon calculator for your marketplace. Both start from what the buyer paid and work down through each platform fee before subtracting your cost of goods, shipping, and packaging, so the result reflects the order rather than the headline price.

Invoicing clients. The freelancer estimator is the one to open. It handles platform fees, payment processing, the tax reserve you decide to set aside, and the unbilled hours that quietly reduce your effective rate.

Working out tax. Start with self-employment tax if you want the figure itself, quarterly estimated tax if you need to know what to send the IRS during the year, and the home office deduction if you work from a dedicated space. Each links to a full guide that explains the rule behind the math.

Selling internationally. The VAT calculator adds or extracts VAT at any rate you set, which is the common requirement for sellers shipping into the UK and EU.

How these tools are maintained

Rates move. Marketplace fees change on notice, and federal tax parameters are adjusted every year. Tax figures come from a versioned dataset that is updated when the IRS publishes new parameters, and published versions are immutable, so a result can always be traced to the data that produced it. Fee schedules are re-checked when a platform announces a pricing change, and the date of the last check appears in each page's source table.

The calculation logic is versioned separately from the data. Each tool displays its formula version, and the validation page records what each version does, the test cases it must satisfy, and a dated log of every material correction. That log is public on purpose: an estimator that never admits a fix is harder to trust than one that shows its history. If a result does not match the method described on the page, there is a link on every calculator to report it against a specific version.

Guides that explain the math

Every calculator has a companion guide that covers the rule behind it in full, with worked examples and citations. Fee guides for sellers live in the guides section, and everything covering federal tax rules lives in the tax guides section. If you would rather understand the calculation before running it, start there and follow the link back to the tool.