HELOC Calculator
How much you can draw on a home equity line, the interest-only payment during the draw period, and the payment shock when the repayment period starts.
HELOC Calculator: with the default inputs, payment jump when repayment begins is $164.57.
What an appraiser would say today, not what you paid.
Everything already secured by the home.
The lender's cap on all liens together. 80–90% is typical.
Not the credit limit — the balance you will actually be carrying.
HELOC rates are variable, usually the prime rate plus a margin.
How much the required monthly payment rises the month the draw period ends.
- Monthly payment during repayment
- $852.07
- Interest-only payment during the draw
- $687.50
- The payment multiplies by
- 1.24×
- Maximum line at this CLTV
- $425,000
- Available credit
- $125,000Maximum line minus your first mortgage balance.
- Interest paid during the draw period
- $82,500
- Interest paid during repayment
- $104,496
- Total interest over the whole line
- $186,996
- Combined loan-to-value after the draw
- 80%
Assumptions
- Payments during the draw period are interest only on the balance you entered; no principal is repaid and no further draws are taken.
- The repayment period fully amortizes the balance at a level payment. Balloon structures, which some lines use instead, are not modelled — check your agreement.
- The rate is held constant within each period. HELOC rates are variable in reality; use the repayment-rate field to test a higher rate.
- Annual fees, inactivity fees, early-closure fees and closing costs are excluded.
- The combined loan-to-value cap and the resulting line are equity tests only; lenders also underwrite income, debt-to-income and credit.
| Year | Phase | Monthly payment | Interest that year | Principal that year | Balance |
|---|---|---|---|---|---|
| 1 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 2 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 3 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 4 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 5 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 6 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 7 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 8 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 9 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 10 | Draw | $687.50 | $8,250 | $0 | $100,000 |
| 11 | Repayment | $852.07 | $8,174 | $2,051 | $97,949 |
| 12 | Repayment | $852.07 | $7,998 | $2,227 | $95,722 |
How this is worked out
The formula
Maximum line = home value × maximum combined loan-to-value Available credit = maximum line − balances already secured by the home Interest-only payment (draw period) = balance × annual rate ÷ 12 Repayment payment = B × r(1+r)^n ÷ ((1+r)^n − 1), n = repayment months Payment shock = repayment payment − interest-only payment
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Home value
- What an appraiser would say today, not what you paid.in dollars · 0 or more · defaults to 500000
- First mortgage balance
- Everything already secured by the home.in dollars · 0 or more · defaults to 300000
- Maximum combined loan-to-value
- The lender's cap on all liens together. 80–90% is typical.a percentage · from 1 to 100 · defaults to 85
- Amount you expect to owe when the draw period ends
- Not the credit limit — the balance you will actually be carrying.in dollars · 0 or more · defaults to 100000
- Interest rate during the draw
- HELOC rates are variable, usually the prime rate plus a margin.a percentage · from 0 to 30 · defaults to 8.25
- Draw period
- A number.from 1 to 20 · whole numbers only · defaults to 10
- Repayment period
- A number.from 1 to 30 · whole numbers only · defaults to 20
- Rate when repayment begins(under More options)
- Set this higher than the draw rate to see what a rate rise does to the shock.a percentage · from 0 to 30 · defaults to 8.25
What you get back
- Payment jump when repayment beginsmain answer
- How much the required monthly payment rises the month the draw period ends.
- Monthly payment during repayment
- Interest-only payment during the draw
- The payment multiplies by
- Maximum line at this CLTV
- Available credit
- Maximum line minus your first mortgage balance.
- Interest paid during the draw period
- Interest paid during repayment
- Total interest over the whole line
- Combined loan-to-value after the draw
What this assumes
- Payments during the draw period are interest only on the balance you entered; no principal is repaid and no further draws are taken.
- The repayment period fully amortizes the balance at a level payment. Balloon structures, which some lines use instead, are not modelled — check your agreement.
- The rate is held constant within each period. HELOC rates are variable in reality; use the repayment-rate field to test a higher rate.
- Annual fees, inactivity fees, early-closure fees and closing costs are excluded.
- The combined loan-to-value cap and the resulting line are equity tests only; lenders also underwrite income, debt-to-income and credit.
About this calculator
A home equity line of credit has two lives. During the draw period — usually ten years — you can borrow up to your limit and the minimum payment is often interest only, which makes a large balance feel almost free. Then the draw period ends, the line closes, and you have to repay the whole balance over the repayment period. The payment does not drift upward. It steps, on one specific month, and the step is the single most misunderstood thing about this product.
The shock, quantified
Carry $100,000 at 8.25%. Interest only, that is $688 a month. When a 20-year repayment period starts, the same balance amortizes at $852 — a 24% jump. Shorten the repayment period to ten years and the payment becomes $1,226, nearly double. And because HELOC rates are variable, the rate that applies when repayment begins is not the rate you signed at: two points higher on that $100,000 over ten years is another $100 a month again. The Rate when repayment begins field under More options lets you price exactly that.
Some lines are worse than this model. A balloon structure ends the draw period with the entire balance due at once rather than amortizing it — the CFPB's own HELOC booklet flags this. Read your agreement for the words "balloon payment" before you assume you get a repayment period at all.
How to use it
Enter what the home is worth now, what you still owe on the first mortgage, and the lender's combined loan-to-value cap — 80% to 90% covers most programs. The amount you expect to owe when the draw period ends is not your credit limit; it is the balance you will realistically be carrying, and it is the number that drives everything else. Use Solve for → Amount to find the balance whose repayment payment you could actually afford.
Reading the results
- Available credit is the line you would qualify for on equity alone. Lenders also look at income and credit, so treat it as a ceiling, not an offer.
- Interest paid during the draw is money that buys no principal reduction whatsoever. Ten years of interest-only on $100,000 is over $82,000, and you still owe $100,000 at the end.
- Combined loan-to-value after the draw is the number the lender watches. Above 90%, a soft housing market can leave you underwater, and lenders are contractually allowed to freeze or cut a line when values fall — which is exactly when people want to draw on it.
Where this breaks down
The model holds the rate flat within each period, so it cannot capture a rate that moves every quarter; use the repayment-rate field to bracket the range instead. It assumes you pay only interest during the draw and never draw again after the balance you entered. Annual fees, inactivity fees and early-closure fees are not modelled, and neither is the interest deduction — since 2018 HELOC interest is deductible only when the money is used to buy, build or substantially improve the home securing the loan, and only if you itemize.
Frequently asked questions
▸How much can I borrow with a HELOC?
Your lender's combined loan-to-value cap times the home's value, minus everything already secured by the home. At an 85% cap on a $500,000 home with a $300,000 mortgage, that is $125,000 — subject also to income and credit.
▸What is payment shock on a HELOC?
The step increase in the required payment on the month the draw period ends and the repayment period begins. Interest-only payments stop and the full balance starts amortizing, so the payment can rise by 25% to well over 100% depending on the repayment term and the rate.
▸What happens at the end of the draw period?
You can no longer borrow, and the balance must be repaid — usually amortized over 10 to 20 years, but some lines require the whole balance as a balloon payment. Check your agreement; the two outcomes are wildly different.
▸Are HELOC rates fixed?
Almost never. They are typically the prime rate plus a margin and reset as prime moves, so the payment during the draw changes with rates and the repayment payment is set by whatever the rate is when repayment starts. Some lenders let you fix a portion of the balance.
▸Is HELOC interest tax deductible?
Only if the proceeds are used to buy, build or substantially improve the home that secures the line, and only if you itemize. Using a HELOC to consolidate credit cards or pay tuition makes the interest non-deductible under current law.
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