There's no single "best" calculator for every firm. It depends on who your clients are. This page doesn't rank products. It lists the calculator types that suit bookkeeping and accounting sites, uses our own free tools as a worked example (we built them, so read it with that in mind), and points to the other kinds of options that exist.
| Calculator | Good for clients who… | Our free example |
|---|---|---|
| Quarterly estimated tax | are newly self-employed and unsure what to set aside | Quarterly tax calculator |
| Home office deduction | work from home and ask "simplified or actual?" | Home office calculator |
| Mileage deduction | drive for work (trades, real estate, delivery) | Mileage log calculator |
| Monthly budget | want personal or household budgeting help | Budget calculator |
| Invoice / estimate generator | are sole traders still invoicing by hand | Invoice · Estimate |
| Hourly rate, margin, break-even | are pricing their services or products | Hourly rate · Margin · Break-even |
Pick two or three that match your clients rather than adding everything.
We make the free tools and the kit mentioned here. We haven't tested other vendors' products, so we don't rate or compare them.
It depends on your clients: quarterly tax, home office, mileage, budget, invoice/estimate, and hourly rate, margin or break-even tools. Pick two or three that match them.
Test it against cases you've worked by hand, check which tax year it uses, where the data goes, branding, cost over time and who maintains it.
For some questions the IRS Tax Withholding Estimator is the right answer: free and authoritative, but not branded to you and visitors leave your site.
For firms: see branded calculators running on a page at the White-Label Calculator Kit demo.