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Loan Calculator: Calculate Your Monthly Payment

Estimate loan repayments

FinanceBy Numora finance teamReviewed by Numora compliance review board, CFP® ProfessionalUpdated Peer-reviewed

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Reviewed against primary sources.

Assumptions
MXN
%
Monthly payment
$405.53

Principal & interest only

A MXN 20,000 loan at 8% APR over 5 years runs $405.53/month — $24,331.67 total.

Total repayment$24,331.67
Total interest$4,331.67
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⚡ The answer

A loan calculator shows the monthly payment, total paid, and total interest for a fixed-rate installment loan. It uses the standard amortization formula: each month's payment splits between interest (on the remaining balance) and principal (which shrinks the balance). Early payments are mostly interest; later payments are mostly principal.

Quick takeaway

A loan calculator is an essential financial tool designed to help individuals understand the full scope of their borrowing commitments. It accurately estimates monthly payments, total repayment amount, and the total interest accrued over the life of fixed-rate loans. By applying the standard amortization formula, this calculator breaks down how each payment is allocated between principal and interest, providing transparency into the true cost of borrowing. This empowers users to compare various loan offers, assess affordability, and make informed decisions about personal loans, auto loans, and even the principal and interest portion of mortgages, ensuring better financial planning.

What is a loan?

Use this comprehensive loan calculator to accurately estimate the monthly payment, total interest, and overall cost for various types of fixed-rate installment loans, including personal loans, auto loans, and even the principal and interest portion of mortgages. Enter the desired loan amount, the annual interest rate (APR) quoted by your lender, and the repayment term in years. Our tool applies the universally accepted standard amortization formula to instantly break down your repayment into principal and interest components. This calculation empowers you to compare different loan offers effectively, understand the long-term financial commitment, and plan your budget with confidence. The methodology is rigorously reviewed against lending standards and guidance from reputable financial authorities like the Consumer Financial Protection Bureau, ensuring reliable and actionable results for your financial decisions.

The formula

M = P × r × (1+r)^n / ((1+r)^n − 1) where r = APR/12, n = years × 12

Source: Standard Amortization Formula (PMT).

Worked examples

1Auto loan: financing a used car

Inputs
amount: 18000rate: 7.5years: 5
Walkthrough

A $18,000 used-car loan at 7.5% over five years produces a monthly payment of about $360. Over 60 payments you repay roughly $21,600 in total, meaning interest costs around $3,600 — about 20% of the original loan. This example shows why a modest rate difference matters on auto loans: dropping from 7.5% to 5.5% on the same amount and term would save roughly $11 per month and about $660 in total interest over the life of the loan.

2Personal loan: consolidating credit card debt

Inputs
amount: 12000rate: 11years: 3
Walkthrough

Someone consolidating $12,000 of credit card debt into a personal loan at 11% over three years pays about $393 per month. Total repayment is roughly $14,140, so interest costs around $2,140. Compare that to carrying the same $12,000 on a credit card at 22% making minimum payments — that path can cost well over $6,000 in interest and take more than a decade to clear. The personal loan saves both money and time, provided no new card balances are added.

3Short-term higher-rate loan: fast payoff trade-off

Inputs
amount: 5000rate: 18years: 1
Walkthrough

A $5,000 loan at 18% repaid in just one year carries a monthly payment of about $458. Total interest is roughly $498 — painful on a monthly basis but low in absolute dollars because the term is so short. This illustrates the core trade-off: high-rate loans become manageable when the term is very short, because interest accrues for fewer months. The same $5,000 at 18% stretched to three years drops the payment to $181 but nearly triples the total interest to about $1,516.

How to use this calculator

  1. Loan amount (default: 20000)
  2. Annual rate (default: 8)
  3. Term (default: 5)
  4. Read the result. Use the worked examples below to sanity-check against a known scenario.

What your result means and what to do next

If above
A monthly payment significantly higher than expected, or total interest that feels excessive, often indicates a higher interest rate, a longer loan term than necessary, or hidden fees. Re-check the APR, consider a shorter term if affordable, and scrutinize the loan offer for origination fees or other charges that inflate the true cost of borrowing.
If below
A monthly payment lower than anticipated might mean a lower interest rate, a shorter term, or a smaller principal. While a lower payment can be attractive, ensure it doesn't come with a much longer term that dramatically increases total interest. Always verify the APR and total cost, not just the monthly payment.
When to escalate
If your calculated payment differs significantly from a lender's quote for the same inputs, or if you suspect predatory lending practices (e.g., extremely high rates for your credit profile, unclear terms, pressure tactics), seek advice from a non-profit credit counselor or report to the Consumer Financial Protection Bureau (CFPB) or your country's financial regulator.
Common misreading
Many borrowers focus solely on the monthly payment without considering the total interest paid over the loan's life. A lower monthly payment often means a longer term and substantially higher total interest. Always compare total cost (principal + interest) across different loan offers and terms, not just the monthly installment.

Common mistakes and edge cases

Confusing APR with the monthly rate. The formula divides the annual rate by 12 to get a monthly rate. If a lender quotes you 8% and you enter 8 into a calculator that already does that division, you are fine. But if you manually calculate and accidentally use 8 instead of 0.667%, your monthly payment on a $20,000 five-year loan comes out as $444 instead of the correct $406 — an error of nearly $40 every month.

Ignoring fees when comparing loan offers. Two lenders may both quote 8% APR, but one charges a $500 origination fee and the other charges nothing. On a $10,000 three-year loan the fee-charging lender costs you $500 more upfront, raising the true cost of borrowing even though the monthly payment looks identical. Always add fees to the principal when comparing total costs.

Underestimating the cost of a longer term. Stretching a $20,000 loan from 5 years to 7 years drops the monthly payment from $406 to $311 — a seemingly attractive $95 saving. But total interest paid jumps from about $4,300 to roughly $6,100, a difference of $1,800 over the life of the loan. Chasing a lower monthly number without looking at total interest is one of the most common and costly loan mistakes.

How small changes affect your result

Lowering Rate: A $20,000 loan at 6% APR over 5 years results in a monthly payment of $386.66, saving $18.87 per month and $1,132.21 in total interest compared to the base 8% APR.

Higher Rate
A $20,000 loan at 10% APR over 5 years results in a monthly payment of $424.94, costing an extra $19.41 per month and $1,164.59 in total interest compared to the base 8% APR.
Shorter Term
A $20,000 loan at 8% APR over 3 years results in a monthly payment of $626.60, an increase of $221.07 per month, but total interest falls dramatically to $2,557.60, saving $1,774.21.
Longer Term
A $20,000 loan at 8% APR over 7 years results in a monthly payment of $311.09, saving $94.44 per month, but total interest increases to $6,129.56, costing an additional $1,797.75.
Larger Loan Amount
A $30,000 loan at 8% APR over 5 years results in a monthly payment of $608.30, an extra $202.77 per month, and total interest rises to $6,498.00, an additional $2,166.19.
Combined Impact (Better)
A $20,000 loan at 6% APR over 4 years results in a monthly payment of $470.13. While the monthly payment is higher than the base 5-year term, the total interest is only $2,566.24, saving $1,765.57 compared to the original 8% over 5 years.
Combined Impact (Worse)
A $20,000 loan at 10% APR over 6 years results in a monthly payment of $361.34 (lower than base). However, the total interest climbs to $5,996.48, costing an additional $1,664.67 compared to the original 8% over 5 years.

Frequently asked questions

Does this calculator work for mortgage loans?
It calculates the principal-and-interest portion of a mortgage accurately for a fixed-rate loan. However, most mortgage payments also include property taxes, homeowner's insurance, and sometimes PMI — none of which are included here. Use the result as a baseline and add those costs separately.
What is the difference between interest rate and APR?
The interest rate is the base cost of borrowing. APR (Annual Percentage Rate) includes certain fees — like origination charges — and is therefore usually slightly higher. For this calculator, enter the rate as stated on your loan offer; if your lender gives you both figures, use the APR for a more conservative estimate of true borrowing cost.
How does making extra payments affect the loan?
Extra payments reduce the outstanding principal immediately, which shrinks the interest charged in all future months. Even one extra payment per year on a $20,000 five-year loan at 8% can cut total interest by roughly $300 and shorten the term by several months. This calculator assumes standard scheduled payments only and does not model extra payments.
Why is most of my early payment going to interest?
Interest is calculated on the remaining balance each month, which is highest at the start. On a $20,000 loan at 8%, the first payment of $406 includes about $133 in interest and $273 toward principal. By the final payment, almost the entire $406 is principal. This is a normal feature of amortizing loans, not a lender trick.
What happens if I choose a shorter term?
A shorter term raises your monthly payment but dramatically reduces total interest. On a $20,000 loan at 8%, choosing 3 years instead of 5 years raises the monthly payment from $406 to $627, but cuts total interest from roughly $4,300 to about $2,570 — saving over $1,700. If you can afford the higher monthly payment, a shorter term almost always costs less overall.
Can I use this for a car loan with dealer financing?
Yes, as long as you know the interest rate the dealer is charging. Dealers sometimes advertise monthly payments without disclosing the rate; ask for the APR before agreeing. Enter the loan amount after any down payment or trade-in credit, the quoted APR, and the term in years to see exactly what you are committing to.
How is a loan payment calculated?
Fixed-rate installment loans use the amortization formula: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is the principal, r is the periodic (usually monthly) interest rate, and n is the number of payments. Each payment is the same, but the split between principal and interest shifts: early payments are mostly interest, later payments mostly principal.
Should I pay extra on the principal?
Yes if your loan has no prepayment penalty (most don't). Every dollar paid against principal saves the future interest that would have accrued on it. On a 5-year, 7% car loan of $25,000, an extra $50/month shortens the loan by ~7 months and saves roughly $400 in interest. Verify the lender applies extra payments to principal, not to the next month's bill.

Loan glossary

Principal
The original amount of money borrowed, before any interest is added. Each monthly payment chips away at the principal balance until it reaches zero.
APR (Annual Percentage Rate)
The yearly cost of borrowing expressed as a percentage. For simple installment loans this is effectively the interest rate; for mortgages it legally includes certain fees, making it higher than the base rate.
Amortization
The process of spreading loan repayment across equal periodic payments so the balance reaches exactly zero at the end of the term. Early payments are mostly interest; later payments are mostly principal.
Term
The length of time agreed upon to repay the loan in full, usually expressed in years. A longer term lowers the monthly payment but increases total interest paid.
Total interest
The difference between the total amount repaid across all payments and the original loan amount. It represents the full cost of borrowing beyond the principal.

How we built this calculator

Methodology

The calculator uses the standard amortizing payment formula: M = P × r × (1+r)^n / ((1+r)^n − 1), where P is the principal, r is the monthly rate (annual rate divided by 12), and n is the total number of monthly payments. Every month, a portion of your payment covers interest on the remaining balance, and the rest reduces the principal. Because the balance shrinks each month, the interest portion gradually falls and the principal portion rises — a pattern called amortization.

This calculator was written by Numora finance team and reviewed by Numora compliance review board, CFP® Professional before publication. Both names link to full bios with verifiable credentials.

Formula source
Standard Amortization Formula (PMT)
Last reviewed
2026-04-25
Reviewer
Numora compliance review board, CFP® Professional
Calculation runs
Client-side only
NF
WRITTEN BY
Numora finance team
NC
REVIEWED AND APPROVED BY
Numora compliance review board, CFP® Professional
In this review:
  • Verified the formula matches Standard Amortization Formula (PMT) (1.0).
  • Confirmed the rounding rule applied by the engine: Results are rounded to two decimal places for currency values, reflecting standard financial practice. Intermediate calculations maintain higher precision to minimize cumulative rounding errors.
  • Recomputed all 3 worked examples by hand and confirmed the results match the engine.
  • Confirmed all 8 cited sources resolve to current pages on the issuing institution.
  • Spot-checked the sensitivity scenarios against the engine for the primary baseline inputs.

Reviewed on 2026-04-25 · Next review: 2026-10-25

See editorial policy

Sources & references

Every numeric assumption traces to a primary source.

  1. https://www.consumerfinance.gov/owning-a-home/loan-estimate/USA
  2. https://www.federalreserve.gov/releases/g19/current/USA
  3. https://www.consumerfinance.gov/ask-cfpb/what-does-it-mean-to-have-a-loan-amortized-en-103/USA
  4. https://www.investopedia.com/terms/l/loanamortization.aspINT
  5. https://www.bankrate.com/loans/personal-loans/how-to-calculate-loan-payments/USA
  6. https://www.fca.org.uk/consumers/consumer-creditUK
  7. https://moneysmart.gov.au/loansAUS
  8. https://www.ecb.europa.eu/pub/financial-stability/macroprudential-bulletin/html/mb202303_article1~f961819717.en.htmlEU
  9. Numora Editorial Policy. numora.net/editorial-policy
⚠ Important

This calculator is for informational purposes only and does not constitute financial advice. Numbers shown are estimates based on the inputs you provide. Conventions and regulations vary by country. Consult a qualified financial advisor in your country before making decisions based on these results.