Finance Calculators

What the finance calculators cover

Finance is the largest category on ToolkitHQ: sixteen calculators covering borrowing, income, everyday money, and long-term planning. Every one is free, runs entirely in your browser, and needs no account. They are built to be used together — a loan payment you work out here slots straight into the same budget as your pay, your tax, and your savings.

Borrowing and debt

• Auto loan — monthly payment, total interest, and a full amortization schedule, with optional extra payments.
• Simple loan — the same payment mathematics without the vehicle-specific tax and trade-in detail.
• Refinance — whether replacing a loan with a new rate actually pays off, and how long the break-even takes.
• Mortgage payoff — how much time and interest extra monthly payments remove from a mortgage.
• Credit card payoff — the snowball and avalanche strategies, side by side, with the interest each costs.
• Lease vs buy — total cost of leasing a car against financing one over the years you keep it.

Income, pay, and household costs

• Salary to hourly — convert pay between annual, monthly, biweekly, weekly, daily, and hourly for any schedule.
• Child support — a simplified income-shares estimate from both parents’ incomes and custody nights.
• Cost of living — compare what the same salary buys in two different locations.

Everyday money

• Tip — gratuity by percentage, with an optional split between diners.
• Sales tax — add tax to a subtotal or reverse it out of a total, with US state base rates built in.
• Stacked discounts — what multiple percentage discounts in sequence actually save, since they do not simply add up.

Long-term planning

• Retirement — how much to save, and what a nest egg could support.
• Investment growth — compound growth and the annual return implied by your starting and ending values.
• Net worth — assets minus liabilities, the one number that summarises your position.

How to use them together

1. Start with the biggest decision. For most people that is a car or a mortgage, so get the payment and total interest first.
2. Convert income to a comparable basis. An hourly rate and an annual salary are hard to compare until you put them in the same units.
3. Check the recurring costs. Sales tax, tips, and stacked discounts are small individually and add up across a year.
4. Look at the long term last. Once the monthly picture is clear, retirement, investing, and net worth show where it is heading.

Which finance calculator should I start with?

Start with the decision that costs the most money. If you are buying a car, get the payment and total interest from the auto loan calculator, then use lease vs buy to confirm financing is the right route at all. If you are comparing job offers, the salary converter makes the numbers comparable before anything else. If you are simply trying to understand your position, net worth is the fastest snapshot and retirement is the longest view.

Common mistakes

• Comparing by monthly payment alone. A longer term lowers the payment and raises the total interest; two identical payments can hide very different costs.
• Ignoring local rates. A state sales tax base rate is rarely the rate you actually pay — county and city add-ons push it higher.
• Treating estimates as final numbers. Child support and tax figures depend on local rules; a calculator gives you a defensible starting point, not an authoritative one.
• Forgetting the non-payment costs. Insurance, maintenance, and fees decide many finance questions more than the headline rate does.

Frequently asked questions

Are the results financial advice?

No. These are estimates for planning and comparison. Anything that depends on your full financial picture, local rates, or tax law should be confirmed with an accountant or adviser. The calculations themselves are exact given the inputs you provide.

Why does my bank quote a different payment?

Banks usually fold in fees, insurance, or a different compounding convention, and they may round differently. If your inputs match theirs, the amortization formula will match too — the gap is almost always in the inputs or the extra charges, not the maths.

Can I save or share a calculation?

Yes. Most tools write their inputs into the page URL, so a bookmarked or copied link reopens with the same numbers, and your last few results are kept locally in the browser.

If you run a business, the earning side of the same equation lives in the business calculators — and when a percentage is what you actually need, the percentage calculator settles it in seconds.