Line of Credit Calculator
Estimate line of credit interest, available credit, and payoff time.
- Last reviewed
- July 8, 2026
- Cost
- Free to use
- Data
- Runs in your browser
Line of Credit Calculator
Methodology
How this calculator handles inputs
This calculator uses the values you enter above and applies the formula explained in the guide below. Results update in the browser and are intended for quick planning, comparison, and sanity-checking.
- Use consistent periods, currencies, and units across inputs.
- Review any assumptions before using the result in a decision.
- Recalculate when rates, prices, tax rules, or business terms change.
Important note
This tool provides general planning information only. It is not tax, legal, financial, accounting, or investment advice. Check the current rules for your location and speak with a qualified professional before making a high-stakes decision.
Guide
How it works
Use this calculator to estimate monthly interest, available credit, and payoff time for a line of credit. It helps you understand the cost of carrying a drawn balance and whether your repayment is enough.
What this calculator does
The line of credit calculator estimates borrowing cost on a revolving credit line.
It uses:
- credit limit
- drawn balance
- annual interest rate
- monthly repayment
The result shows monthly interest, available credit, and estimated payoff time if repayments exceed interest.
How to use the line of credit calculator
Enter your credit limit, current drawn balance, annual interest rate, and planned monthly repayment. The calculator checks available credit and simulates payoff if the repayment is high enough.
Use it for planning only because many credit lines have variable rates or fees.
Line of Credit Formula
Monthly interest = drawn balance x annual interest rate / 12
Available credit = credit limit - drawn balance
New balance = balance + interest - repayment
Example calculation
If:
- Credit limit = 20,000
- Drawn balance = 5,000
- Annual interest rate = 12%
- Monthly repayment = 500
Then:
Monthly interest = 5,000 x 12% / 12 = 50
Available credit is 15,000 before any new draws.
What is a line of credit?
A line of credit is flexible borrowing that lets you draw up to a limit, repay, and borrow again. Interest is usually charged only on the drawn balance.
It can be useful, but revolving debt can grow if repayments are too low.
Interpreting your result
If repayment is less than monthly interest, the balance may not fall. A repayment above interest is needed to reduce principal.
When to use this calculator
Use this calculator when you want to:
- estimate monthly interest
- check available credit
- test repayment plans
- review revolving debt
Common mistakes
Common mistakes include:
- repaying interest only
- ignoring variable rates
- drawing more while repaying
- treating credit limit as income
FAQs
Is interest charged on the full limit?
Usually no. Interest is commonly charged on the drawn balance.
What if repayment is below interest?
The balance may not reduce and can grow.
Can rates change?
Many lines of credit have variable rates.
Is this financial advice?
No. It is a planning estimate only.
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