Finance Calculators

What belongs in the finance category?

These calculators cover the money decisions most people actually face: car loans, sales tax, hourly pay, leasing vs. buying, and child support. Each one takes a few inputs and returns a concrete number you can use immediately — no account, no signup, no email gate.

What you can calculate

• Car loan payments — monthly payment, total interest, and an amortization schedule with optional extra payments.
• Sales tax — add tax to a price or reverse it out of a total, with U.S. state base rates built in.
• Salary to hourly pay — convert an annual salary into hourly, weekly, and monthly figures for any hours-per-week schedule.
• Lease vs. buy — compare the total cost of leasing versus financing a car over the same ownership window.
• Child support — a simplified income-shares estimate from both parents’ incomes, custody nights, and child count.

How to use the results

1. Start with the biggest line item. For a car purchase that’s the monthly loan payment — budget it, then check the total interest to see what the term really costs.
2. Cross-check any dollar figure that depends on a local rate. Sales tax varies by state, county, and city, so confirm the combined rate for your address.
3. Compare before committing. Run the same car through the lease-vs-buy calculator if you’re weighing a lease, and convert job offers to hourly pay before comparing salaries.
4. Treat estimates as a starting point. Child support in particular is a guideline here — your state’s official formula, attorneys, and court orders will set the final number.

Which finance calculator should I use first?

Start with the decision that costs the most money. For most people that’s a car — so get the monthly payment and total interest from the auto loan calculator, then use the lease-vs-buy tool to check whether financing is even the right route. If you’re comparing job offers, the salary-to-hourly converter is the fastest way to make the numbers comparable.

Common mistakes

• Ignoring local rates. A state sales tax base rate is rarely the rate you actually pay — city and county add-ons can push it several points higher.
• Comparing loans by monthly payment alone. Two identical payments can hide wildly different total interest depending on term length.
• Forgetting the non-payment costs. Leasing looks cheap monthly until you account for the lower residual value you get nothing from.

These tools are built to work together — a car loan payment feeds straight into the same budgeting math as a steady salary. If you run a business or bill for work, the invoice generator sits in the Business category but handles the earning side of the same equation.