Finance & Business
Calculators for payments, fees, and business math. — 13 tools available.
Finance and business calculators handle the everyday money math that freelancers, investors, and small businesses face. The compound interest calculator lets you visualize how an investment grows year-by-year with monthly contributions, including an inflation-adjusted mode for real purchasing-power planning. Payment processor fee calculators show exactly how much to charge so you receive your target amount after PayPal or Stripe deducts their cut. These tools run entirely in your browser — your financial figures are never sent to any server. Whether you're planning for retirement, pricing a freelance project, or reconciling a payout, these calculators give you instant, accurate answers without a spreadsheet.
13 Finance & Business Tools
Freelance Hourly Rate Calculator
Calculate your minimum freelance hourly rate, day rate, and weekly retainer based on income goals, expenses, and the true cost of unbillable hours.
Compound Interest Calculator
Calculate compound interest growth with monthly contributions. Interactive year-by-year chart with inflation-adjusted mode.
PayPal & Stripe Fee Calculator
Calculate PayPal and Stripe transaction fees. Enter the amount you want to receive and get the exact amount to charge.
Loan Calculator
Calculate monthly loan payments and view a full amortization schedule with principal and interest breakdown.
Sales Tax Calculator
Add or remove sales tax for any US state. Pre-loaded with all 50 state tax rates.
Car Payment Calculator
Calculate your monthly car payment with APR, down payment, trade-in, taxes, and fees. Includes amortization table and total cost breakdown.
Margin Calculator
Calculate gross profit margin, markup percentage, and revenue needed. Includes break-even calculator and industry margin benchmarks.
Investment Calculator
Calculate investment growth with compound interest and monthly contributions. Shows year-by-year breakdown and total returns.
Retirement Calculator
Calculate how much you need to retire using the 4% rule. See if you are on track and how contributions affect your retirement date.
Income Tax Calculator
Estimate your 2025 federal income tax based on taxable income, filing status, and deductions. Shows marginal vs. effective tax rate and FICA breakdown.
Invoice Generator
Create professional invoices with itemized line items, discounts, taxes, and auto-save. Print as PDF or copy as plain text. Stores data in browser.
ROI Calculator
Calculate simple and annualized ROI (CAGR) with S&P 500 benchmark comparison. Includes profit/loss display and 3 example presets.
Budget Calculator
Budget your income using the 50/30/20 rule. See recommended allocations for needs, wants, and savings. Includes custom split override.
Frequently Asked Questions
Is my financial data private when using these calculators?
Yes. All finance calculators run entirely in your browser. No dollar amounts, interest rates, salary figures, or any other financial data is ever transmitted to a server. You can verify this by opening your browser's DevTools Network tab — no requests are made during calculations. Closing the tab erases all inputs.
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on the principal), compound interest causes your investment to grow exponentially over time. The more frequently interest compounds (daily, monthly, annually), the faster the balance grows. Albert Einstein reportedly called it the eighth wonder of the world.
How do payment processor fees work?
Payment processors like Stripe and PayPal typically charge a percentage of the transaction amount plus a fixed fee per transaction (e.g., 2.9% + $0.30). This means the fee scales with the payment size. To receive a specific net amount, you need to charge more than that amount to cover the fee — our payment fee calculator computes the exact gross amount to charge.