Interest is a two-sided coin. You can earn it or pay it, depending on the financial vehicle you’re using. Investment accounts earn interest, so you want that interest to compound over time. Debt carries an interest expense. Simple interest is preferable in that scenario. This guide explains how these two models differ and why you need to know about them.
Understanding how this works, and specifically how daily simple interest loans operate, can help you make smarter financial decisions and keep more money in your pocket. Compound interest on an investment account can create a significant income stream. Simple interest is often preferable for borrowers because interest is generally calculated on the remaining principal balance, which can reduce total interest when payments are made on time or early.
Let’s examine the reasons why.
The Simple Interest Formula
Simple interest is calculated using the following equation:
I = PRT
Each variable in the formula represents a key piece of the loan or investment:
- P = Principal: The initial amount borrowed or invested. This is the base figure on which interest is calculated.
- R = Annual Interest Rate (as a decimal): The yearly interest rate is expressed as a decimal. For example, an 18% interest rate becomes 0.18 in the formula.
- T = Time Period (in years): The length of time the money is borrowed or invested, expressed in years. A 6-month loan would be expressed as 0.5.
The result, I, is the total interest charged or earned over the loan or savings period. Unlike compound interest, simple interest is always calculated on the original principal. It doesn’t “grow on itself” like compound interest. That’s good for debt but bad for investments.
How to Calculate Simple Interest: Step-by-Step Examples
Example 1: Calculating Interest on a Car Loan
Suppose you take out a $10,000 car loan at an annual interest rate of 7% for 3 years:
- P = $10,000
- R = 0.07
- T = 3
I = $10,000 × 0.07 × 3 = $2,100
Over the life of the loan, you would pay $2,100 in interest, bringing the total repaid to $12,100.
Example 2: Calculating Interest Earned in a Savings Account
Now suppose you deposit $5,000 into a savings account that pays 4% simple interest annually, and you leave it untouched for 2 years:
- P = $5,000
- R = 0.04
- T = 2
I = $5,000 × 0.04 × 2 = $400
After two years, you would earn $400 in interest, bringing your total balance to $5,400.
Calculating the Total Amount to Be Repaid (A = P(1 + RT))
To find the total amount owed (principal + interest), use this expanded formula:
A = P(1 + RT)
Using the car loan example above:
A = $10,000 × (1 + 0.16 × 3) = $10,000 × 1.48 = $14,800
This gives you the cost of the loan, which can be helpful when comparing financing options. The 1st Franklin loan calculator can be used as a starting point to explore estimated payments and potential loan scenarios, though actual terms and amounts may vary.
Simple Interest vs. Compound Interest: The Key Differences
This isn’t as complicated as it sounds. With simple interest, you always pay or earn interest on the original principal of the account. Compound interest is applied to the total balance owed, including interest earned in previous periods. Investment accounts grow more quickly with compounding, but debt becomes more expensive. Here’s a visual breakdown:
| Simple Interest | Compound Interest | |
|---|---|---|
| How It’s Calculated | On the original principal only | On principal + accumulated interest |
| Growth Over Time | Linear: grows at a steady rate | Exponential: accelerates over time |
| Best for Borrowers? | Yes: lower total interest paid | No: interest accumulates faster |
| Best for Savers? | No: slower earnings growth | Yes: interest earns interest |
| Common Uses | Personal loans, auto loans, and some mortgages | Savings accounts, credit cards, investments |
From a borrower’s perspective, simple interest can be more favorable because the borrowing cost is fixed. That’s why term loans can offer fixed monthly payments. The rate is set at the beginning of the loan term, and it doesn’t change. Compounding is less predictable because interest rates change over time, sometimes from month to month. That makes budgeting more difficult.
When Is Simple Interest Used in the Real World?
You’re already familiar with simple interest if you’re making payments on a car loan or short-term personal loan. Auto dealers can offer “low APRs” because auto loan lenders typically offer simple interest rates. Banks, credit unions, and online lenders also tend to use simple interest rates for their loan products. Compounding is not normally seen on the debt side.
Think about this from the borrower’s perspective. If the interest on a loan is calculated on the original principal, you can see the exact cost of the loan before you sign the loan agreement. You can also break that cost down by the number of months in the loan agreement. This is great for comparing loan offers with different rates and terms.
Short-term loans with 12 to 60-month terms are ideal for this type of loan structure. The fixed rate helps borrowers budget their payments. That’s critical when you need funds quickly and can only afford to make small monthly payments. With a simple-interest loan, you may have the option of a longer loan term to lower those monthly payments.
Daily Simple Interest Loan
A daily simple interest loan is a financial product that’s similar to a standard simple interest loan, but the interest accrues daily. It doesn’t compound, so you’ll only be charged interest on the principal balance owed, but it does add up over time. On a positive note, you can significantly reduce your interest expense by making payments more frequently. Here’s how that works:
- Paying down principal: Loan agreements usually require monthly or lump-sum payments. Daily simple interest loans can be repaid at any time you carry an unpaid balance. Each time you make an “extra” payment, your interest expense goes down. This helps you pay your loan off in a shorter period of time.
- Missing payments costs you: The downside of daily simple-interest loans is that missed payments are more costly. Additional interest on the unpaid principal accrues each day you remain in arrears. It’s not compounded, so you’re not paying interest on interest, but you are paying interest on the amount of that unpaid monthly payment.
- Late payments carry additional consequences: Beyond the extra interest that accumulates on an unpaid balance, late payments may also trigger late fees. Making payments on time or early, when possible, is especially important on a daily simple interest loan because the daily accrual means every day counts.
If you want to understand exactly how your loan balance would break down, review the 1st Franklin loan checklist before you apply to make sure you have everything you need.
Frequently Asked Questions about Simple Interest
