About PlainCalc
PlainCalc is a set of 24 free financial calculators built around one idea: a good calculator shows the whole answer and explains it. Not just a monthly payment, but the taxes and insurance behind it. Not just a number, but the formula, the assumptions, and what to do next.
Who is behind PlainCalc
PlainCalc is built and maintained by an independent small-business owner. PlainCalc is maintained by a small independent team focused on making everyday money calculations easier to understand. Every calculator shows its formula, assumptions, and data sources so visitors can check the numbers themselves. Reach the team at hello@plaincalc.com.
Why we built it
The most-used financial calculators on the web were designed fifteen or twenty years ago. They still work, but they hide results behind a “Calculate” button, skip the costs that make up half of a real payment, and bury the answer under ads. We wanted tools that update as you type, work on a phone, remember your numbers, and can be shared with a single link, without asking for an email address or an account.
Methodology
Every calculator uses standard, published formulas, and the relevant formula is written out on each page:
- Loans and mortgages use the standard amortization formula with monthly compounding. Extra payments are applied to principal in the month they’re made.
- Savings and retirement simulate month by month rather than using closed-form approximations, so contribution timing and compounding frequency are handled exactly.
- Federal income tax applies the IRS brackets, standard deduction, and Social Security wage base for the stated tax year. State income tax uses a representative effective rate per state and is clearly labeled as an estimate.
- Sales tax uses state rates plus population-weighted average local rates; users can enter an exact local rate.
Pages that depend on annually updated figures (tax brackets, contribution limits, sales tax rates) show the year those figures were verified. We review them each January and when the IRS publishes new inflation adjustments in the fall.
Sources
- Internal Revenue Service: annual inflation adjustments (Rev. Proc.), retirement plan limits.
- Social Security Administration: wage base and FICA rates.
- Tax Foundation and state departments of revenue: sales tax and income tax rates.
- Federal Reserve Survey of Consumer Finances: net worth benchmarks.
- Freddie Mac, Bankrate, and the Federal Reserve for typical interest-rate ranges cited in explanations.
What we don’t do
We don’t give personalized financial, tax, or legal advice. The calculators are educational tools; for decisions that matter, confirm the figures with a licensed professional. We don’t sell leads, we don’t require sign-ups, and we don’t upload what you type. Saved calculations live in your own browser’s storage. See the privacy policy for the details.
How the site is funded
PlainCalc is free to use and supported by a small number of clearly marked advertisements. Ads never affect results, and we don’t accept payment to recommend any financial product.
Corrections
Found a mistake? We take accuracy seriously and fix confirmed errors quickly. Contact us with the page and the issue.