OmniCalc

Loan Calculator

Finance

Free loan calculator — monthly payment, total interest, and amortization for any loan

M = P * [r(1+r)^n] / [(1+r)^n - 1]

Where:

MMonthly Payment — payment amount
PPrincipal — loan amount
rMonthly Rate — annual rate / 12
nPayments — total number of payments
Extra payments▾

Whether you're financing a car, taking out a personal loan, or evaluating a home equity line of credit, the monthly payment is only part of what you need to know. The total interest paid over the life of the loan — often more than the principal itself — is the number that determines whether a loan is genuinely affordable or a financial trap.

Our free loan calculator computes your monthly payment instantly and generates a full amortization schedule showing exactly how each payment breaks down between principal and interest, month by month, until the loan is paid off. Change any input and the results update instantly — making it easy to compare different loan amounts, terms, and rates side by side.

Use this calculator to evaluate any fixed-rate loan: personal loans, auto loans, student loans, medical financing, or any installment debt with regular monthly payments.

Why Loan Calculator Matters

Loans are one of the most consequential financial products most people use, yet the math behind them is opaque. A lender who quotes you "just $299/month" on a 72-month auto loan may be charging you $4,500 more in total interest than a 48-month option with a higher monthly payment. Without a calculator, most borrowers cannot evaluate this tradeoff.

According to the Federal Reserve's Consumer Credit report, total consumer debt in the United States exceeds $5 trillion, and the average American household carries loans across multiple categories. Understanding the true cost of each loan — including total interest paid — is essential to managing this debt responsibly.

The amortization schedule is particularly powerful: it reveals that in the early months, the vast majority of each payment goes to interest rather than principal. This "front-loading" of interest is why paying even a small extra amount each month can dramatically reduce total cost and payoff time.

The Loan Calculator Formula, Explained

M = P[r(1+r)^n] / [(1+r)^n – 1]

Where: M = monthly payment, P = principal loan amount, r = monthly interest rate (annual rate ÷ 12), n = total number of monthly payments (years × 12).

Example: $20,000 loan at 8% annual rate for 5 years. Monthly rate r = 0.08/12 = 0.00667. Payments n = 60. M = 20,000 × [0.00667 × (1.00667)^60] / [(1.00667)^60 – 1] = $405.53/month.

Total paid over 5 years: $405.53 × 60 = $24,332. Total interest: $4,332.

The amortization schedule breaks down each of those 60 payments: payment 1 allocates $133.33 to interest and $272.20 to principal. By payment 60, only $2.69 goes to interest. This is why early payoff saves so much — you avoid months of high-interest early payments.

How to Use the Loan Calculator: Step by Step

  1. Enter the loan amount

    Input the total amount you plan to borrow (the principal). For a car, this is the purchase price minus your down payment and trade-in value. For a personal loan, it's the amount requested.

  2. Set the interest rate

    Enter the annual interest rate quoted by the lender. This is typically the APR for installment loans. Make sure you're using the same rate basis for any comparison (APR to APR).

  3. Choose the loan term

    Enter the repayment period in years (or months). Shorter terms mean higher monthly payments but lower total interest. Longer terms lower the monthly payment but significantly increase total interest paid.

  4. Review the amortization schedule

    Expand the full schedule to see how much of each payment goes to principal vs. interest. This is where you'll see the front-loading of interest that affects early payoff strategy.

  5. Test early payoff scenarios

    Enter an extra monthly payment amount to see how much you can save in interest and how many months early you can pay off the loan. Even $50/month extra makes a significant difference.

Loan Calculator Examples: Real-World Scenarios

1

Auto Loan — 60 Month vs. 72 Month Comparison

Daniel is buying a $28,000 car and has been offered two loan options: 5.9% for 60 months or 5.9% for 72 months. He wants to know the true cost difference.

Principal:$28,000
Rate:5.9% annual
60-month payment:$540.17/month
72-month payment:$461.54/month

Calculation

60-month: $540.17 × 60 = $32,410 total | 72-month: $461.54 × 72 = $33,231 total

Result

60 months: $4,410 in interest. 72 months: $5,231 in interest. The 72-month loan costs $821 more in interest AND leaves him "underwater" (owing more than the car's value) for longer. The $78.63/month "savings" costs him nearly $1,000 over the life of the loan.

2

Personal Loan — Debt Consolidation

Maria has $12,000 in credit card debt at 22% APR and is evaluating a personal loan to consolidate at 9.5% for 36 months.

Amount:$12,000
Personal loan rate:9.5%
Personal loan term:36 months
Credit card APR:22%

Calculation

Personal loan: M = $384.46/month, total paid = $13,840, interest = $1,840 | Credit card minimum (est. 2%): ~$240/month initial, ~9 years to payoff, ~$8,500 in interest

Result

Personal loan saves approximately $6,660 in interest and 5+ years of payments. Monthly payment increases $144/month but the math is clear: consolidation is the right move.

3

Student Loan — Graduated vs. Standard Repayment

Alex has $45,000 in federal student loans at 6.5% and is choosing between the standard 10-year plan and an income-driven plan (longer term).

Balance:$45,000
Rate:6.5%
Standard plan:10 years
Extended plan:20 years

Calculation

Standard: $509/month, total paid $61,080, interest $16,080 | Extended: $335/month, total paid $80,400, interest $35,400

Result

The extended plan costs $19,320 more in interest — over double. However, the $174/month saved may be necessary early in a career. Use our calculator to find the break-even point where income-driven payments become more affordable than aggressive paydown.

Common Mistakes to Avoid

  • Focusing only on monthly payment, not total cost — a longer term lowers the payment but always increases total interest. Compare both numbers before deciding.
  • Ignoring origination fees — many personal loans charge 1–8% origination fees that come out of your loan proceeds or are added to the balance. These effectively raise the APR.
  • Not factoring in prepayment penalties — some auto loans and personal loans charge fees for early payoff. Check the terms before making extra payments.
  • Using APR and APY interchangeably — for loans, use APR. For savings, APY is what matters. They measure different things.

Tips & Tricks

  • Extra payments go entirely to principal, dramatically accelerating payoff. An extra $100/month on a $20,000 5-year loan at 8% cuts 8 months off the term and saves $476 in interest.
  • Make bi-weekly instead of monthly payments if your lender allows. You'll make 26 half-payments (= 13 full payments) per year instead of 12, paying off a 5-year loan in under 4.5 years.
  • Get pre-approved before shopping for a car or major purchase — knowing your rate and monthly limit prevents dealers from structuring deals around the payment rather than the total price.

Every loan has a true cost that goes far beyond the monthly payment. Use our loan calculator to see the full amortization schedule before you borrow, to compare competing offers accurately, and to find the optimal extra payment strategy for paying down existing debt. The Consumer Financial Protection Bureau's loan tools provide additional unbiased guidance on evaluating loan offers.

Loan Calculator — Frequently Asked Questions

Related Calculators

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ROI Calculator

calculate return on investment

Authoritative References

CFPB — Owning a Home Loan Tools

consumerfinance.gov — Official loan comparison tools

Federal Reserve — Consumer Credit Data

federalreserve.gov — Current consumer loan rate benchmarks

NerdWallet — Personal Loan Rates

nerdwallet.com — Current lender rate comparison

External links open in a new tab. OmniCalc.us is not affiliated with these organisations.

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