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Finance Calculators

Loans, interest, savings, investment and personal money planning.

75 calculators in this category.

A Guide to Finance Calculators

Money questions are rarely about arithmetic. The arithmetic of a mortgage payment is a single line of algebra. What makes the question hard is that the answer depends on assumptions you did not know you were making, and most calculators bury them.

The seventy-five calculators here are grouped by the decision you are actually trying to make. Each one states its assumptions on the page, shows the steps, and where a quantity has no closed-form answer it solves for it numerically rather than pretending a rough formula is exact. This guide points you at the right group and warns you about the places where the standard approach goes wrong.

Mortgages and property

Eleven calculators, and the order matters. Work out what you can borrow before you fall in love with a house: the Mortgage Affordability Calculator starts from income and commitments, and the Down Payment Calculator turns a savings position into a purchase price.

Then the Mortgage Calculator for the payment itself, with the Closing Costs Calculator for the sum people routinely forget until a week before completion. The Home Equity Calculator tracks what you own as the balance falls, and the Refinance Calculator answers whether moving your loan is worth the fees, which is a break-even question rather than a rate comparison.

Three cover decisions rather than payments. Rent vs Buy and Rent vs Sell weigh total cost over a holding period instead of comparing a rent against a payment, which is the usual mistake. The Seller Financing Calculator handles the case where the owner is the lender.

For investors, the ARV Calculator estimates after-repair value and the House Flipping Calculator nets it against holding and selling costs.

Loans and credit

Seven loan calculators plus four for debt. The Loan Calculator is the general one and runs in four directions: it will solve for the payment, the amount you can borrow, the term, or the rate you are actually being charged. That last mode exists because a rate is the one quantity in the set with no closed-form solution, so it is found by bisection rather than approximated.

The Amortization Calculator shows the whole schedule, which is the clearest way to see how little of an early payment touches the principal. The Loan Payoff Calculator prices the effect of paying extra, and the Personal Loan and Student Loan calculators handle the terms specific to each.

The Auto Loan Calculator and Car Affordability Calculator deal with a loan secured against an asset that is falling in value faster than the balance, which is why the auto loan calculator reports when you are underwater and when you climb out. On a typical 84-month loan with no deposit, that is month fifty.

For existing debt, the Debt to Income Calculator gives the ratio lenders judge you by, while Debt Snowball and Debt Consolidation compare strategies on total interest and time rather than on which feels better. The Credit Card Payoff Calculator shows what a minimum payment really costs, which is the single most persuasive figure in personal finance.

Interest, and why there are five calculators for it

The Simple Interest Calculator and Compound Interest Calculator are the foundation. The Interest Rate Calculator solves backwards for the rate.

The other two exist because of a distinction that costs people real money. APR includes fees and is what a borrowing cost should be compared on; APY includes compounding and is what a savings return should be compared on. A rate quoted without saying which convention it uses is not comparable to anything.

The Rule of 72 Calculator is the shortcut, and it is close enough to be worth knowing: at 3 percent inflation money halves in buying power in about 23 years.

Investing

Ten calculators. The Investment Calculator and Stock Return Calculator cover growth and realised return, ROI the general ratio, and the Dividend Calculator income rather than appreciation.

The Bond Yield Calculator is the most technical here. Yield to maturity assumes every coupon is reinvested at the same yield, and the calculator reports the return if you do not reinvest at all, so you can see how much of the quoted yield depends on that assumption. Both figures are annualised on the same basis, which sounds obvious and is where most implementations go wrong: compare an effective annual return against a nominal semiannual yield and a zero-coupon bond appears to have a reinvestment gap, which is impossible, since it has no coupons to reinvest.

The Dollar Cost Averaging Calculator compares staged buying against a lump sum, the Covered Call Calculator prices the trade-off in capping your upside, and the Basis Points Calculator converts the unit rates are quoted in. The Inflation Calculator is the one to run before you admire any long-run return.

Time value of money

Five calculators for the idea that a sum has a different value depending on when it arrives. Present Value and Future Value are the two directions, the Annuity Calculator handles a stream rather than a single sum, and NPV and IRR are the two ways to judge a project. IRR has no closed form either, so it is solved numerically and the calculator says so.

Retirement and saving

The Retirement Calculator is the general projection, with the 401(k), IRA and Pension calculators for specific vehicles. The Barista FIRE Calculator handles partial retirement, where part-time income reduces how much the portfolio has to carry.

Nearer term, the Emergency Fund Calculator sizes the buffer, Savings and Savings Goal work forwards and backwards from a target, and the CD Calculator prices a fixed term.

Income and budgeting

The Salary Calculator and Hourly to Salary Calculator convert between pay bases, the Paycheck Calculator works out take-home, and the Overtime Calculator handles premium rates.

For planning, the Budget Calculator is the general one, the 50/30/20 Budget Calculator applies the common rule, and the Net Worth Calculator gives the position rather than the flow.

Tax

Tax is the one area where a calculator must be explicit about jurisdiction, because the rules are not similar enough to generalise. There are separate calculators for the UK, the US and Pakistan, plus capital gains for the UK and the US, and UK stamp duty.

The Pakistan calculator shows something worth seeing: the surcharge on high salaries creates a genuine cliff. Take-home falls by about Rs 179,440 as you cross the threshold, and does not recover until roughly Rs 10.39 million of taxable income. A smooth-curve calculator cannot show you that, because it is not smooth.

The VAT Calculator includes flat-rate schemes, where a scheme is only worth taking if the flat rate stays below the standard rate divided by one plus that rate. The Sales Tax Calculator handles the combined state and local case, where applying one rate then another instead of their sum overstates the tax by the product of the two. The Property Tax Calculator works from assessed value and millage.

A standing caution: a tax calculator is only as current as the rates it was written against, and rates change every year. Check the year stated on the page before you rely on a figure.

Legal and employment money

Five calculators for situations people meet once and have no reference for. Severance Package, Workers Compensation, Wage Garnishment, Settlement Tax and Chapter 13 Bankruptcy. Each one states the statutory basis it works from. None of them is legal advice, and all of them are worth running before a conversation with someone who can give you some.

Vehicle value

Three calculators that answer different questions about the same car. Car Scrap Value works from curb weight and the price per ton. Vehicle Scrap Value breaks the same car down by metal, which gives a higher and better-supported figure when you are negotiating. Vehicle Diminished Value is for a car that has been repaired after an accident and is worth less than an equivalent one that has not.

Before you rely on any of these

Every calculator here is an estimate built on stated assumptions, and the assumptions are where the money is. A projection at 7 percent is not a forecast. A tax figure is a guide to the order of magnitude, not a filing. A loan comparison depends on fees that may not be in the quoted rate.

What these calculators do give you is the arithmetic, shown step by step, with the assumption written next to the answer. That is enough to arrive at a conversation with a broker, accountant or lender knowing which questions to ask, which is a better use for them than treating the output as a decision.