Guides
Notes that sit
next to the tools
Worked numbers, the decision they support, and where the inputs come from.
These notes tie several calculators together. Each tool page still has its own formula explanation. The guides are the worked examples and the decisions that sit across more than one page.
- Pennsylvania paycheck and car tax. The 3.07% state tax, the local line people leave at zero, and 6% versus Philadelphia and Allegheny sales tax.
- How to read a car deal. Out-the-door price, the loan term, depreciation, fuel, and a tire-size check.
- Freelance taxes and what to charge. A 1099 year, a quarterly set-aside, and the hourly rate that can pay it.
- Household money. A mortgage, an affordable price, a debt order, and a retirement balance in today’s dollars.
- Home project quantities. Paint, concrete, mulch, flooring, and a room air conditioner.
- Solar payback. Why the incentive box starts at zero, and when to switch to PVWatts.
Numbers were checked against the calculator code and the sources linked on each page. Last updated October 29, 2026.
Last updated: October 29, 2026. Estimates only. Not tax, legal, financial, or professional advice. See the terms.