Line of Credit Payment Calculator
Estimate the first monthly payment, interest, changing balance, and possible payoff time for a revolving line of credit. Choose an interest-only payment, a fixed monthly amount, or a percentage-of-balance rule with a minimum, and optionally model one future draw. This is an educational scenario—not a lender quote, approval decision, or exact statement calculation.
fixed monthly payment
- Projected payoff
- 4 years, 9 months
- First-month interest
- $166.67
- Interest in first 12 months
- $1,961.01
- Balance after 12 months
- $18,461.01
- Total interest through payoff
- $5,654.96
- Total modeled payments
- $28,154.96
- Payment in draw month
- $500.00
- Final modeled payment
- $154.96
Modeled monthly LOC schedule
The model adds any selected draw before interest, then applies the selected payment rule at month-end.
Formula and monthly method
The monthly rate is r = APR ÷ 12 ÷ 100. For month t, interest is It = (Bt−1 + Dt) × r, where B is the opening balance and D is the optional draw. The payment rule Q is interest only, the entered fixed amount, or the greater of an entered balance percentage and dollar minimum. The actual payment is capped at the amount owed, and the ending balance is Bt = Bt−1 + Dt + It − Pt.
The model uses equal monthly periods, adds the optional draw before interest, applies payment afterward, and holds APR and the payment rule constant. It excludes fees. Actual accounts may use daily or average-daily balances, different minimum formulas, rate tiers, floors, fees, and changing variable rates.
Worked example
Start with a $20,000 balance at 10.00% APR, pay a fixed $500 per month, and draw $2,500 at the start of month 6. The first modeled payment is $500 and first-month interest is $166.67. Interest in month 6 is $173.38 after the draw.
Under those constant assumptions, the balance is $18,461.01 after 12 months and reaches zero in 57 months. Modeled interest through payoff is $5,654.96, total payments are $28,154.96, and the final payment is $154.96.
How to interpret the result
Interest-only payments generally do not reduce principal. A fixed payment below monthly interest causes the balance to grow, and percentage-based payments can change every month. Kalcue shows payoff and lifetime interest only when the modeled balance reaches zero within 600 months; otherwise it avoids presenting a partial 50-year total as lifetime cost.
Personal LOC versus HELOC
A personal line of credit is generally unsecured. A home equity line of credit is secured by the home, so failure to repay can put the home at risk. HELOCs can also separate a draw period from a repayment period, change the payment method, use a variable rate, or require a balloon payment. This calculator models one constant monthly rule and does not reproduce those contractual transitions.
Frequently asked questions
Does this calculate my lender's exact minimum payment?
No. Minimum-payment formulas, balance methods, fees, rounding, and payment allocation vary. Use your agreement and current statement for the contractual amount.
Why does interest-only show no payoff?
The modeled payment equals that month's interest, so it does not reduce principal. A future draw increases the principal still owed.
How does the percentage-and-minimum option work?
It uses the greater of the entered percentage of that month's balance after any modeled draw or the entered dollar minimum. Some creditors instead use interest plus principal or another formula.
How is the optional draw handled?
It is added once at the start of the selected month before interest and payment. Actual interest can depend on the exact posting day and balance-computation method.
Can my APR or payment change?
Yes. Many HELOCs use variable rates, and payment rules may change between draw and repayment periods. This model holds both constant.
Does the estimate include fees or determine approval?
No. It excludes annual, transaction, draw, late, appraisal, closing, and other fees and makes no eligibility, credit-limit, lender, or approval determination.
Official sources and review
- Consumer Financial Protection Bureau: Personal lines of credit
- Consumer Financial Protection Bureau: Home equity lines of credit
- Consumer Financial Protection Bureau: Regulation Z § 1026.40
- Consumer Financial Protection Bureau: Regulation Z Appendix G balance-computation clauses
- Consumer Financial Protection Bureau: What you should know about HELOCs
Formula, source claims, worked example, and explanatory content reviewed August 31, 2026. Actual line-of-credit terms can change; confirm the current APR, payment rule, balance method, fees, and draw/repayment provisions in the creditor's disclosures and account agreement.