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calculatorInterest rate calculator for simple interest loan

Confused about your interest charge? If you have an interest-bearing loan, or what is sometimes referred to as a simple interest loan, Web math created an interest rate calculator that breaks down the formula to help simplify the calculation.

How does a loan calculator factor your interest?

Great question, the formula loan calculators use is I = P * r *T in layman’s terms Interest equals the principal amount multiplied by your interest rate times the amount in years.

For example


  • P is the principal amount, $3000.00.
  • r is the interest rate, 4.99% per year, or in decimal form, 4.99/100=0.0499.
  • t is the time involved, 3….year(s) time periods.
  • So, t is 3….year time periods.

To find the simple interest, we multiply 3000 × 0.0499 × 3 to get that:

The interest is: $449.10

Usually, now, the interest is added to the principal to figure some new amount after 3 year(s),
or 3000.00 + 449.10 = 3449.10. For example:

  • If you borrowed the $3000.00, you would now owe $3449.10
  • If you loaned someone $3000.00, you would now be due $3449.10
  • If owned something, like a $3000.00 bond, it would be worth $3449.10 now.

Click here to use this helpful loan calculator and use it as a reference when calculating simple interest.

How do you calculate a loan payment?

It’s understandable you may want to determine if a loan is affordable and a loan calculator or a bit of math can help you find out what your monthly payments may be. Calculators are great for quick answers so let’s look into how to calculate your monthly loan payment with a monthly payment calculator.

However to do that first you must identify which type of loan you have.

There are two types, interest-only loans where you only service the loan by paying interest and amortizing loans which you pay down the loan balance over a set period of time.

For simply interest loans you can use this loan calculator.

For amortizing loans you can use this personal loan calculator.

If you’re interested in a personal loan today you can apply here at Mariner Finance.


Still confused? Contact your local Mariner Finance branch today to speak with a knowledgeable staff member about your account.

Blog posts are for informational purposes only.

†We offer personal loans from $1,000 to $25,000, with loans terms from 12 to 60 months. Minimum and maximum amounts dependent on an applicant’s state of residence and the underwriting of the loan. Loans between $1,500 and $15,000 may be funded online. Loans greater than $15,000 or less than $1,500 are funded through our branch network. Specific interest rates and fees are determined as permitted under applicable state law and depend upon loan amount, term, and the applicant’s ability to meet our credit criteria, including, but not limited to, credit history, income, debt payment obligations, and other factors such as availability of collateral. Not all rates and loan amounts are available in all states. Additional fees may apply to some loan offers; some state required and/or permitted fees may be treated as prepaid finance charges. Any such charges shall be in addition to the loan amount requested and/or approved and shall be fully disclosed to the applicant on his/her loan agreement. Not all applicants will qualify for the lowest rates or larger loan amounts, which may require a first lien on a motor vehicle not more than ten years old titled in the applicant’s name with valid insurance. Our loan by phone and online closing process requires a compatible mobile or computer device on which you can access your email and electronic documents. Not all loan types are eligible for loan by phone or online loan closing.


To help the government fight the funding of terrorism and money laundering activities, Federal law requires all financial institutions to obtain, verify, and record information that identifies each person who opens an account. As a result, under our customer identification program, we must ask for your name, street address, mailing address, date of birth, and other information that will allow us to identify you. We may also ask to see your driver's license or other identifying documents.


*The process uses a “soft” credit inquiry to determine whether a loan offer is available, which does not impact your credit score. If you continue with the application process online and accept a loan offer, or are referred to a branch and continue your application there, we will pull your credit report and credit score again using a “hard” credit inquiry. This “hard” credit inquiry may impact your credit score.


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