HELOC Repayment & Payment Shock Calculator
Estimate what happens when a HELOC leaves the draw period. The calculator projects remaining draws and principal payments, then converts the ending balance into a repayment payment, stressed payment, interest cost, and possible balloon.
Repayment-period monthly payment$492.37
- Current interest-only minimum
- $354.17
- Balance when repayment begins
- $50,000.00
- Last draw-period payment
- $354.17
- Payment jump at transition
- $138.20
- Payment increase
- 39.02%
- Rate-stressed monthly payment
- $552.70
- Balloon balance at maturity
- $0.00
- Interest paid during repayment
- $38,626.56
- Credit-line utilization at transition
- 50%
Repayment by year
| Year | Principal paid | Interest paid | Balance |
|---|---|---|---|
| 1 | $1,724.60 | $4,183.84 | $48,275.40 |
| 2 | $1,877.04 | $4,031.40 | $46,398.37 |
| 3 | $2,042.95 | $3,865.49 | $44,355.42 |
| 4 | $2,223.53 | $3,684.91 | $42,131.89 |
| 5 | $2,420.07 | $3,488.37 | $39,711.82 |
| 6 | $2,633.98 | $3,274.46 | $37,077.84 |
| 7 | $2,866.80 | $3,041.64 | $34,211.05 |
| 8 | $3,120.20 | $2,788.24 | $31,090.85 |
| 9 | $3,395.99 | $2,512.44 | $27,694.85 |
| 10 | $3,696.17 | $2,212.27 | $23,998.69 |
| 11 | $4,022.88 | $1,885.56 | $19,975.81 |
| 12 | $4,378.46 | $1,529.97 | $15,597.35 |
| 13 | $4,765.48 | $1,142.96 | $10,831.87 |
| 14 | $5,186.70 | $721.73 | $5,645.16 |
| 15 | $5,645.16 | $263.28 | $0.00 |
Assumes draw-period interest is paid each month and does not capitalize into principal.
Uses monthly interest periods; many HELOC agreements calculate interest from daily balances.
How to use this calculator
- Enter the current HELOC balance and credit limit.
- Add the months left in the draw period, expected future draws, and any planned principal paydown.
- Enter the draw-period APR, expected repayment APR, repayment term, amortization period, and rate stress.
- Read the transition balance, normal repayment payment, payment jump, stressed payment, and balloon estimate.
How the HELOC repayment payment is calculated
A HELOC often has two phases. During the draw period, many borrowers pay interest while they can still borrow against the line. When the draw period ends, new borrowing stops and the balance must be repaid over the remaining contractual term. That change can create payment shock because the bill moves from mostly interest to principal and interest.
This calculator first projects the remaining draw months one month at a time. In each month it adds the expected draw, capped by the credit limit, calculates interest on the balance after the draw, applies the planned principal paydown, and carries the ending balance forward.
gross balance = min(credit limit, prior balance + monthly draw)
draw payment = gross balance x draw APR / 12 + principal paid
ending balance = gross balance - principal paid
After the last draw month, the remaining balance becomes the opening repayment balance. The normal repayment payment uses the standard amortization formula:
payment = balance x monthly rate / (1 - (1 + monthly rate)^-months)
If the repayment APR is zero, the payment is simply the balance divided by the amortization months. The rate-stressed payment uses the same formula after adding the selected stress increase to the repayment APR.
What moves the result most
The transition balance is usually the biggest driver. Continued draws raise the repayment payment, while principal paydowns before the draw period ends lower it. The repayment APR also matters because HELOC rates are commonly variable. A two percentage point rate increase can make the payment jump larger even if the balance does not change.
The amortization period controls the scheduled payment, while the repayment term controls how long payments are actually made before maturity. If the amortization period is longer than the repayment term, the scheduled payment may leave a balloon balance due at maturity. If the amortization period is shorter than the repayment term, the calculator stops repayment interest once the balance reaches zero.
What this calculator leaves out
Actual HELOC agreements can use daily-average-balance interest, minimum payment floors, annual fees, transaction charges, rate caps, rate floors, or lender-specific rounding. This estimate assumes monthly interest, draws at the start of each modeled month, and every draw-period interest charge paid in cash instead of added to principal.
Worked example
Suppose the current HELOC balance is $50,000, the credit limit is $100,000, and there are 24 months left in the draw period. With no further draws, no principal paydown, an 8.5% draw APR, an 8.5% repayment APR, a 15-year repayment term, and a 15-year amortization period, the current interest-only minimum is $354.17.
The projected balance when repayment begins is still $50,000. The repayment-period payment is $492.37, so the transition jump is $138.21, or about 39.02%. With a 2 percentage point rate stress, the estimated payment rises to $552.68. Because the repayment term and amortization period are both 15 years, the balloon balance is $0 and repayment interest is about $38,626.27.
Common questions
Why can a HELOC payment rise when the draw period ends?
During the draw period, the required payment may be interest-only or mostly interest. In repayment, the balance has to amortize, so each payment includes principal. The payment can rise further if the variable rate is higher when repayment begins.
How is a HELOC repayment-period payment calculated?
The calculator uses the projected transition balance, expected repayment APR, and payment amortization period. It applies the standard monthly amortization formula, with a straight-line principal calculation when the APR is zero.
What happens if I keep drawing from the HELOC?
Expected draws increase the projected transition balance until the credit limit is reached. Any draw amount beyond the available credit is not added to the balance, and the calculator shows a note for the unfunded amount.
Can I reduce payment shock by paying principal during the draw period?
Yes. Principal paid before repayment begins lowers the balance that has to amortize later. It also reduces draw-period interest in later projected months because interest is calculated on a smaller balance.
What is a HELOC balloon payment?
A balloon is the principal still owed at contractual maturity after the scheduled repayment payments. It can happen when the payment is based on an amortization period longer than the actual repayment term.
Is a HELOC payment based on daily or monthly interest?
Many lenders calculate HELOC interest from daily balances. This calculator uses monthly rates and assumes draws occur at the start of each projected month, so it is an estimate rather than a statement of the lender bill.