# Loan Interest Calculator

URL: https://speedycalculator.com/calculators/finance/loan-interest/
Last updated: 2026-10-25

> The loan interest calculator works out the total interest you will pay on a loan – amortizing (equal payments) or simple interest repaid at the end – with the monthly payment, total repaid and interest as a share of the loan.

## Inputs

- Loan type
- Loan amount
- Interest rate (%)
- Loan term (years, months)

## Results

- Monthly payment
- Total interest
- Total repaid
- Interest as a share of the loan
- Interest in the first month

## Formula

```
Amortizing: payment = pmt(i, n, L), interest = payment × n − L
Simple interest (repaid at the end): interest = L × r × years
```

## Explanation

Interest depends on three things: the amount, the rate and the time. Halving the term of an amortizing loan more than halves the interest because the balance falls faster.

### How to use the Loan Interest Calculator

- **Loan type**
- **Loan amount**
- **Interest rate**
- **Loan term**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Choose the loan type, enter the amount, interest rate and term.

### Tips

- Compare loans by APR and total cost, not just the monthly payment.
- Extra payments go straight to principal and can save a lot of interest.
- Pay off the highest-rate debt first if you want to save the most money.
- Check for prepayment penalties before paying a loan off early.

### Common mistakes to avoid

- Stretching a loan term to lower the payment without seeing the extra interest.
- Paying only the minimum on credit cards.
- Forgetting fees that are rolled into the loan.

### Inputs explained

FieldWhat to enterLoan typeChoose one: Amortizing (equal monthly payments), Simple interest, repaid at the endLoan amountAmount in your currencyInterest rateIn %Loan termUnits: years, months

### What each result means

- **Total repaid** = [Loan amount] + [Total interest]
- **Interest as a share of the loan** = [Total interest]÷[Loan amount]×100
- **Interest in the first month** = [Loan amount]×[Interest rate]÷1200

### Example values

How the main result changes when **Loan amount** changes and everything else stays at the example values above:

Loan amountTotal interest5,000723.957,5001,085.9310,0001,447.912,5001,809.8815,0002,171.8620,0002,895.81

## Worked example

Inputs — Loan type: Amortizing (equal monthly payments); Loan amount: $10,000; Interest rate: 9 %; Loan term: 3 years.

Results — Monthly payment = $318.00; **Total interest = $1,447.90**; Total repaid = $11,447.90; Interest as a share of the loan = 14.48 %; Interest in the first month = $75.00.

## FAQ

**How do I calculate loan interest?**
For equal payments: payment × months − loan amount.

**What's the difference between simple and amortizing interest?**
Amortizing interest falls as you repay; simple interest is on the full amount.

**How can I pay less interest?**
Borrow less, get a lower rate, choose a shorter term or pay extra.

**What formula does the Loan Interest Calculator use?**
Amortizing: payment = pmt(i, n, L), interest = payment × n − L.


## Sources

- [Consumer Financial Protection Bureau](https://www.consumerfinance.gov/)