Pick the tool by the money question
Everyday US money questions cluster into four jobs. US Money Ops is the Tools.Town cluster for answering them fast — no spreadsheet, no signup, all in-browser.
| Question | Tool |
|---|---|
| ”What does this cost with tax?” / “How much of this total is tax?” | Sales Tax Calculator |
| ”What does $28/hr make per year?” / “What hourly rate equals $75k?” | Hourly to Salary Calculator |
| ”What price gives me a 40% margin on this cost?” | Margin & Markup Calculator |
| ”How long until this investment doubles?” | Rule of 72 Calculator |
| ”How many units until I cover fixed costs?” | Break-Even Calculator |
| ”What’s simple interest on this short loan?” | Simple Interest Calculator |
| ”When will this card balance clear?” | Debt Payoff Calculator |
Sales tax: add vs extract
Two directions, same math. Add when you have a pre-tax price and need the checkout total. Extract when you have a receipt total and need to back out the tax — common for expense reports and bookkeeping. The Sales Tax Calculator does both; walkthrough in Back Out Sales Tax From a Receipt.
Pay conversion: hourly ↔ salary
Job posts mix hourly and annual figures. The Hourly to Salary Calculator converts both directions with custom hours/week and weeks/year — so freelancers can exclude unpaid vacation instead of blindly assuming 40×52. Quoting a client rate? See Convert a Salary Target to a Freelance Hourly Rate. For Indian CTC breakdowns, use the Salary Calculator instead.
Pricing: margin is not markup
A 25% margin and a 25% markup produce different prices from the same cost — mixing them up silently underprices your product. Read Margin vs Markup, Explained, then price with the Margin & Markup Calculator. Worked example: Price a Product With a Target Margin.
Growth: doubling time in your head
Years to double ≈ 72 ÷ annual return %. The Rule of 72 Calculator also shows the exact natural-log answer so you can see where the approximation drifts. Deep dive: The Rule of 72 Explained.
Break-even & simple interest
Sellers need units to cover rent and materials — Break-Even Calculator with Find Break-Even Units for a Product. Short loans that do not compound use Simple Interest Calculator — Calculate Simple Interest on a Short Loan.
Related clusters
- Buying a home? The mortgage ecosystem starts at the Mortgage Calculator.
- Splitting a restaurant bill: Tip Calculator · discounts: Discount Calculator.
- Indian tax and investing lives in the India Finance cluster — GST Calculator, SIP Calculator, Income Tax Calculator.
Disclaimer: All tools in this cluster provide educational estimates only — not tax, legal, or investment advice.