Plain definition
Interest is the price charged for using borrowed money. It is calculated under the agreement’s rate, balance basis, and time basis; it is separate from principal repayment and may be separate from arrangement, commitment, or late-payment fees. A rate that sounds small can still create a material cash cost when the balance is large, the borrowing lasts longer than expected, or the rate changes.
Illustrative example
Monetary examples use Saudi riyals (SAR). The same principles apply in other currencies.
A company borrows . Its agreement charges 1% for a stated month on the outstanding balance, producing of interest for that month. If it pays at month end, may reduce principal and may be the interest charge. The business needs cash for both amounts, but only the principal component lowers next month’s balance under this illustration.
| Outstanding principal | |
|---|---|
| Monthly interest rate as decimal | |
| Interest charge |
Actual interest depends on the contract, including its day-count method, variable-rate terms, compounding, and fees.
Why it matters
Interest affects affordability before a loan ever matures. A founder who looks only at principal payments can understate the cash need and the cost of a delayed collection period. Separating rate, balance, and time shows which assumption caused the expense and makes lender comparisons more honest.
Practical consequence
Record the rate type, reference rate if variable, balance basis, payment dates, compounding terms, and all fees from the agreement. Recalculate the forecast when the balance or rate changes. Compare total cash cost and conditions across offers, not the displayed rate alone; the example is a simplified monthly illustration, not a substitute for the lender calculation.