Understand the true cost of borrowing
Whether you're buying a car, consolidating debt, or comparing loan offers — these calculators show you the full picture before you sign anything.
Auto Loan Calculator
Estimate your monthly car payment and total loan cost
How Your Auto Loan Payment Is Calculated
Your monthly payment is determined by three factors: the loan amount (vehicle price minus down payment), the interest rate (APR), and the loan term. Lenders use a standard amortization formula ensuring each payment covers the month's interest plus a portion of principal. In early months, more goes toward interest; by the end, nearly all reduces the principal.
A larger down payment directly reduces your loan amount, lowering both your monthly payment and total interest paid. Even a 10–20% down payment can save hundreds or thousands. A shorter term means higher monthly payments but significantly less total interest.
Personal Loan Calculator
Monthly payment, total interest, and your payoff date
Understanding Personal Loan Rates and Terms
Personal loans are unsecured — they don't require collateral — which is why their rates tend to be higher than secured loans. Lenders set your APR based on credit score, income, DTI ratio, and loan amount. Borrowers with scores above 720 typically qualify for the most competitive rates. Always compare APR rather than stated interest rate, since APR includes fees and gives a true picture of the loan's cost.
Credit Card Payoff Calculator
See exactly how long and how much it costs to eliminate your balance
Why Credit Card Interest Is So Costly — and How to Beat It
Credit cards carry some of the highest interest rates of any consumer debt, with the average U.S. APR exceeding 20%. Interest compounds daily — your balance is multiplied by the daily rate (APR ÷ 365) every single day. Even small balances grow quickly if you only make minimum payments.
On a $5,500 balance at 22.99% APR, paying only the minimum (approximately 2% of balance) would take over 20 years to pay off and cost more than $7,000 in interest. Paying a fixed $200/month pays it off in just over 3 years with under $2,000 in interest. The avalanche method (highest APR first) minimizes total interest; the snowball method (smallest balance first) builds momentum.
Put your money to work for you
Compound interest and consistent saving are the two most powerful forces in personal finance. These calculators show you exactly how powerful they can be.
Compound Interest & Savings Calculator
Watch your money multiply with the power of compound interest
The Power of Compound Interest — and Why Starting Early Matters
Compound interest earns returns on both your principal and the interest you've already accumulated. Over long time horizons, this creates exponential growth. The single most powerful variable isn't the interest rate — it's time. Starting 10 years earlier can more than double your ending balance due to the additional compounding cycles.
Common sources of compound growth include high-yield savings accounts (currently 4–5% APY), index funds tracking the S&P 500 (historically ~7–10% annualized after inflation), and tax-advantaged accounts like 401(k)s and IRAs.
Savings Goal Planner
Find out exactly when you'll reach your savings target
Setting and Reaching Financial Goals
Research consistently shows that people with specific, measurable financial goals save more than those who save "whatever is left over." This calculator turns an abstract goal into a concrete monthly action plan. Consider automating your contributions on payday — automatic transfers dramatically increase savings consistency because the money moves before you can spend it.
Know your numbers before you borrow
Lenders look at these metrics first. Understanding them helps you qualify for better rates and avoid financial surprises.
Debt-to-Income Ratio Calculator
Know your DTI before applying for a mortgage or any major loan
What Your DTI Ratio Means for Loan Approval
Your debt-to-income ratio compares total monthly debt obligations to gross monthly income. A DTI of 37% means 37 cents of every dollar you earn goes toward debt payments. For conventional mortgages, most lenders prefer DTI at or below 43%, with strongest terms reserved for borrowers under 36%. FHA loans may allow DTIs up to 50% in some cases.
To improve your DTI before applying for a major loan, focus on paying down existing debt and avoid taking on new obligations. Increasing income through raises or a second earner on the application also helps significantly.
Emergency Fund Calculator
How much you need saved and how long it will take to build it
Why an Emergency Fund Is Your Most Important Financial Safety Net
An emergency fund is money set aside for unexpected financial shocks — a job loss, medical bill, car repair, or home emergency. Without one, even a small surprise forces many people into high-interest credit card debt. Most financial experts recommend 3 to 6 months of essential living expenses. If you have variable income or more dependents, aim for 6 to 12 months. Keep it in a high-yield savings account — separate from your checking account but accessible within 1–2 business days.
Understand the concepts behind the numbers
Every calculator on this page is built on fundamental financial principles. Understanding these concepts helps you make better decisions — not just today, but for decades to come.
Amortization Explained
Amortization is the process of paying off a loan through regular payments over time. Each payment covers both interest for that period and a portion of the principal. In early payments, most goes toward interest. In later payments, most reduces the principal. This is why making extra payments early in a loan has a dramatic effect — it removes dollars that would have compounded as interest for years.
The Credit Card Minimum Payment Trap
Credit card minimum payments are deliberately designed to keep you in debt as long as possible. At 22.99% APR, paying only the minimum on a $5,500 balance could take over 20 years and cost $7,000+ in interest. The card company earns far more from a minimum-payment customer than from one who pays in full. Always pay more than the minimum — ideally the full balance every month.
The Debt-to-Income Ratio and Lending
Lenders use DTI to assess risk. A high DTI signals that you may struggle to handle additional debt payments. Most conventional mortgage lenders cap at 43% DTI, meaning if more than 43 cents of every dollar you earn already goes to debt, you'll likely be denied or offered worse rates. Knowing your DTI before applying gives you time to pay down debt and strengthen your application.
The Power of Compound Interest Over Time
Einstein reportedly called compound interest the eighth wonder of the world. At 7% annual return, money doubles roughly every 10 years (the Rule of 72: divide 72 by the rate to find doubling time). A 25-year-old who invests $300/month until 65 ends up with nearly twice as much as a 35-year-old who invests the same amount — despite only 10 more years of contributions. Time is the most valuable financial asset you have.
Building Your Emergency Fund First
Before paying extra on loans or investing, most financial advisors recommend building at least a 3-month emergency fund. The reason: without one, any unexpected expense forces you into high-interest debt, which undoes all your other financial progress. Think of the emergency fund as the foundation — without it, everything built on top is unstable. Once it's funded, redirect that monthly savings toward debt payoff or investing.
Goal-Based Saving vs. Passive Saving
Research from behavioral economics consistently shows that people with specific, written savings goals save 2–3x more than those who save "whatever is left over." The key is specificity: not "I want to save more" but "I want $50,000 for a down payment in 4 years, which means saving $833/month." This calculator converts vague intentions into precise monthly actions. Automation — having transfers happen automatically — is the single most effective implementation strategy.
Frequently Asked Questions
Explore our full suite of free tools
PrimeTools.app is home to all our free calculators — mortgage, personal finance, health, GPA, insurance, and more. All free, no sign-up required.