Is it better to pay off debt or invest?

It depends on the interest rate of the debt compared with the return you can reasonably expect after tax. Paying off a credit card charging 20% is a guaranteed 20% return, which few investments match. Low-rate debt is a closer call, and keeping an emergency fund and capturing any employer retirement match usually come first.

How much should I have in an emergency fund?

A common guideline is three to six months of essential expenses, more if your income is irregular or you support others. The right amount depends on job stability, insurance and other resources. The Emergency Fund Calculator turns your own expenses into a target and a savings timeline.

What does the 4% rule mean?

It is a guideline from research on historical US market returns: withdrawing about 4% of a portfolio in the first year of retirement, then adjusting that amount for inflation, has historically lasted around 30 years in most periods tested. It is a planning starting point, not a guarantee, and many planners adjust it for longer retirements or current conditions.

Why do compound and simple interest differ so much over time?

Simple interest is paid only on the original principal, while compound interest is also paid on interest already earned. The gap is small at first but grows every period. Over decades, compounding can produce several times the amount of simple interest at the same rate.

Are these calculators financial advice?

No. They apply standard formulas to the inputs you provide and are meant for estimates and comparisons. Actual loan terms, tax liabilities and investment returns depend on details they cannot know, so confirm important decisions with a lender, tax professional or financial adviser.

Financial Math calculators

Financial calculators here cover borrowing (loans, mortgages, credit cards and refinancing), saving and investing, retirement accounts and withdrawals, pay and income tax, and business measures such as break-even, NPV and IRR. They show the formula and assumptions behind each result so you can compare options rather than accept a single number.

69 tools · Updated October 21, 2026

Showing 69 tools

$401(k) & Roth IRA CalculatorRetirement$8,000/yr, 22% tax now, 18% laterTraditional by $30,227

$Amortization CalculatorLoans and debt$300,000 at 6.5% over 30 years$1,896.20 a month

$Annuity CalculatorRetirement$300,000 over 25 years at 5%$1,753.77 a month

$APR CalculatorLoans and debt$10,000 at 6%, $300 fee, 36 months8.057% APR

$Auto Loan CalculatorLoans and debt$35,000 car at 7.5% for 60 months$660.25 a month

$Bill SplitterBudgeting, saving and everyday money4 people by order, 20% tip$32.16 to $62.06 each

$Bond Price CalculatorInvesting and valuation$1,000 5% bond, 10 yr, 4.5% yield$1,039.91

$Break-Even CalculatorPay, tax and business$3,200 fixed, $9.50 cost, $28 price173 units a month

$Budget CalculatorBudgeting, saving and everyday money$3,605 planned of $4,225 take-home$620 left to assign

$CAGR CalculatorInvesting and valuation$10,000 to $18,000 in 6 years10.29% a year

$Capital Gains Tax CalculatorPay, tax and business$30,000 long-term gain, $60,000 income$3,667.50 tax

$Car Lease vs Buy CalculatorLoans and debt$34,500 car: lease or buy over 36 monthsLeasing saves $1,705

$CD CalculatorBudgeting, saving and everyday money$10,000 CD at 4% APY for 12 months$10,400.00

$CD Ladder CalculatorBudgeting, saving and everyday money$30,000 in a 3-rung ladder, 1 to 3 years$34,465.19

$Closing Cost CalculatorMortgages and property$400,000 home, $80,000 down$90,276 cash to close

$College Savings CalculatorBudgeting, saving and everyday money$300/mo from age 5 for $25,000/yr college52% of college covered

$Compound Interest CalculatorBudgeting, saving and everyday money$10,000 + $200/mo at 5% for 10 years$47,526.55

$Credit Card Payoff CalculatorLoans and debt$5,000 at 22%, paying $200 a month34 months

$Crypto Profit CalculatorInvesting and valuation0.5 coin, $45,000 to $65,000$9,725.00 profit

$Currency ConverterBudgeting, saving and everyday money1,000 at 0.873 vs 0.900 mid-market3% markup

$Debt Payoff CalculatorLoans and debt4 debts, $29,700, $200 extra a monthDebt-free in 3 yr 9 mo

$Debt-to-Income CalculatorLoans and debt$2,340/mo debt on $84,000 a year33.4% DTI

$Depreciation CalculatorPay, tax and business$50,000 asset, 7 years, double declining$14,285.71 in year 1

$Dividend CalculatorInvesting and valuation200 shares paying $0.50 a quarter$400.00 a year

$Dollar-Cost Averaging CalculatorInvesting and valuation$500 a month for 12 months$49.60 average cost

$DRIP CalculatorInvesting and valuation100 shares at $50, 3% yield, 20 yr189.58 shares

EOQEconomic Order Quantity CalculatorPay, tax and business1,200 units/yr, $50/order, $5/unit to hold154.9 units per order

$Emergency Fund CalculatorBudgeting, saving and everyday money6 months of $3,000 expenses$18,000

$FIRE CalculatorRetirement$48,000 a year at a 4% withdrawal rate$1,200,000

$Freelance Rate CalculatorPay, tax and business$85,000 take-home, 46 weeks a year$133.30 an hour

$Fuel Cost CalculatorBudgeting, saving and everyday money420 miles at 28 mpg, $3.45/gal$51.75 in fuel

$GST / VAT CalculatorPay, tax and business100 plus 10% GST110.00 with tax

$Home Affordability CalculatorMortgages and property$110,000 income, $50,000 down$359,763 home

$Hourly to Salary CalculatorPay, tax and business$25 an hour, 40 hours a week$52,000 a year

$HSA CalculatorRetirement$4,400 into an HSA, 22% bracket$1,525 tax saved

$Income Tax CalculatorPay, tax and business$80,000 salary, single, 2026$8,770 federal tax

$Inflation CalculatorBudgeting, saving and everyday moneyCost of $1,000 in 20 years at 3% inflation$1,806.11

$Investment CalculatorInvesting and valuation$10,000 + $500/mo at 6% for 30 years$562,483

$IRR CalculatorInvesting and valuation$100,000 in, $155,000 back over 5 yearsIRR 17.6%

$Loan Comparison CalculatorLoans and debt$25,000: 7.5%/5 yr, 6.9%/6 yr, 6.5%/7 yr5 yr loan saves $1,127

$Loan Payment CalculatorLoans and debt$20,000 at 7% for 60 months$396.02 a month

$Meeting Cost CalculatorPay, tax and business7 people for 60 minutes$667.83 a meeting

$Mortgage CalculatorMortgages and property$256,000 at 5% over 25 years$1,496.55 a month

$Mortgage Points CalculatorMortgages and property2 points on $400,000 at 7%+$6,091 after 7 years

$Mortgage Refinance CalculatorMortgages and property$300,000 from 7% to 6.25%+$6,851 after 7 years

$Net Worth CalculatorBudgeting, saving and everyday money$498,000 of assets, $295,000 of debts$203,000 net worth

$NPV CalculatorInvesting and valuation$100,000 in, 5 years of returns at 10%NPV $10,857.74

$Options Pricing CalculatorInvesting and valuation$100 call on a $100 stock, 30 days, 25% vol$3.02

$Overtime Pay CalculatorPay, tax and business46 hours at $22 an hour$1,078.00 for the week

$Paycheck CalculatorPay, tax and business$3,000 every two weeks, single$2,450.12 take-home

$Portfolio RebalancerInvesting and valuationRebalance $45,000 to 50/30/20Sell $2,500 US stocks

$Present Value CalculatorInvesting and valuation$10,000 in 10 years at 5%$6,139.13

$Price per Square Foot CalculatorMore financial math tools$450,000 for 1,800 sq ft$250.00 per sq ft

$PTO Accrual CalculatorMore financial math tools120 h a year, 20 h now, 13 paychecks80.00 hours

$Rent Split CalculatorMore financial math tools$2,400 rent, rooms of 200, 150, 120 sq ft$955 / $776 / $669

$Rent vs Buy CalculatorMortgages and property$400,000 home or $2,200 rent, 7 yearsRenting wins by $22,370

$Rental Property CalculatorMortgages and property$250,000 rental at $2,100 a month$11 a month cash flow

$Retirement Savings CalculatorRetirement$800 a month from 35 to 65, $60,000 saved$1,314,000

$RMD CalculatorRetirement$500,000 IRA at age 73 in 2026$18,867.92 RMD

$ROI CalculatorInvesting and valuation$10,000 grows to $18,000 in 5 years80% ROI

$Salary Negotiation CalculatorPay, tax and business$120,000 vs $130,000 offer over 4 yearsOffer B by $57,221

$Salary to Hourly CalculatorPay, tax and business$75,000 a year, 40 hours a week$36.06 an hour

$Savings Goal CalculatorBudgeting, saving and everyday money$20,000 in 3 years, $2,000 saved$465.38 a month

$Savings Withdrawal CalculatorRetirement$40,000/yr from $1,000,000 at 5%Lasts all 30 years

$Simple Interest CalculatorBudgeting, saving and everyday money$10,000 at 5% for 3 years$1,500.00 interest

$Social Security CalculatorRetirementBorn 1966, $5,000 AIME, claiming at 67$2,345 a month

$Student Loan CalculatorLoans and debt$35,000 loans, $55,000 income, RAP plan$229.17 a month

$Subscription Cost CalculatorMore financial math tools6 subscriptions, from streaming to the gym$98.40 a month

$Tip CalculatorBudgeting, saving and everyday money$85 bill, 18% tip$15.30 tip

Which one do I need?

I want my monthly mortgage payment including taxes and insuranceMortgage Calculator I want to see how much house I can afford on my incomeHome Affordability Calculator I want to see how much of each loan payment is interestAmortization Calculator I have several debts and want a payoff plan and a debt-free dateDebt Payoff Calculator I want to see how savings grow with compound interestCompound Interest Calculator I want to know if I am saving enough for retirementRetirement Savings Calculator I want my take-home pay after taxes and deductionsPaycheck Calculator I want to know if a project is worth it from its cash flowsNPV Calculator

The time value of money

Nearly every tool in this category rests on one idea: a dollar today is worth more than a dollar later, because it can earn a return in the meantime. Compounding grows money forward (future value), and discounting brings future money back to today (present value). The Compound Interest and Present Value calculators show each direction, and the Rule of 72 gives a quick check: at about 6% a year, money roughly doubles in 12 years.

APR and APY express rates differently. APR is the yearly cost of borrowing including certain fees, while APY includes the effect of compounding within the year. When comparing savings accounts or CDs, compare APY; when comparing loans, compare APR, and use the APR Calculator to see how fees change the true cost.

Borrowing: payments, interest and payoff

An amortizing loan has a fixed payment, but its split changes over time: early payments are mostly interest and later ones mostly principal. The Amortization Calculator lays out every payment, and it makes clear why extra principal payments early in a loan save the most interest.

For several debts, two common strategies are the avalanche (pay the highest rate first, which minimizes interest) and the snowball (pay the smallest balance first, which builds momentum). The Debt Payoff Calculator compares them. Before applying for a mortgage, check your debt-to-income ratio, which lenders use alongside credit score and down payment to judge affordability.

Investing and retirement planning

Growth projections depend heavily on the assumed rate of return, so run any investment or retirement estimate with a cautious rate as well as an optimistic one. Inflation matters too: the Inflation Calculator shows how purchasing power erodes, and real returns (after inflation) are what determine future spending power.

Account type affects how much you keep. The 401(k) and Roth IRA Calculator compares paying tax now versus later, the RMD Calculator estimates required withdrawals, and the Savings Withdrawal and FIRE calculators test how long a portfolio might last. Tax rules and contribution limits change, so confirm current figures with the IRS or a qualified adviser before acting.

Questions people ask

The interest rate is the cost of borrowing the principal alone. APR adds certain required fees, such as origination charges or mortgage points, and expresses the total as a yearly rate. Two loans with the same interest rate can have different APRs if their fees differ.

Guides

Compound Interest: Formula, Frequency and the Rule of 72