HELOC calculator

Credit line available on your home, interest-only payments while drawing and repayments afterwards.

Home value

Mortgage balance

Most you can borrow in total

% of value

Amount drawn (blank = the whole line)

Interest rate (variable)

% a year

Draw period

years

Repayment period

years

About the heloc calculator

Credit line available on your home, interest-only payments while drawing and repayments afterwards.

Part of SmartCalcy’s mortgage & real estate tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.

How to use the heloc calculator

What it calculates and when to use it

Estimate the credit line a HELOC could give you, the interest-only payment while you draw, and the repayment once the draw period ends.

How to use it, step by step

Enter the home value, mortgage balance and combined loan-to-value limit.
Enter the interest rate and the draw and repayment periods.
Enter how much you plan to draw, or leave it blank to use the whole line.

What each input means

Draw period – The years during which you can borrow and pay interest only.
Repayment period – The years over which the balance is repaid afterwards.
Interest rate – HELOC rates are variable. This estimate holds the rate fixed.

How to read the results

Interest-only payment – Balance × monthly rate during the draw period.
Payment after the draw period – A repayment calculated over the repayment term.
Total interest – Interest across both periods.

The formula

Line = value × limit − mortgage. Draw payment = balance × rate ÷ 12. Repayment = balance × r ÷ (1 − (1 + r)^−n) over the repayment months.

A worked example

On a 400,000 home with a 240,000 mortgage and an 85% limit, the line is 100,000. At 8.5% the interest-only payment is 708.33 a month, then repayment over 20 years is 867.82 a month. Interest over the whole term is about 193,278.

Assumptions and limits

The full line is drawn on day one and the rate never changes.
Annual fees and minimum draws are excluded.

Common mistakes

Underestimating how much the payment rises after the draw period.
Treating a variable rate as fixed.

Frequently asked questions

Is the credit line the same as the amount I should borrow?

No. Borrow only what you need, since the home secures the debt.

Interest-only payment while drawing

£708.33

then £867.82 a month for 20 years

Details

Credit line available: £100,000.00
Amount used in this estimate: £100,000.00
Payment in the repayment period: £867.82
Interest over the whole term: £193,277.58
Total repaid: £293,277.58

HELOC rates normally move with a base rate, so real payments will change. This estimate holds the rate fixed and assumes the whole amount is drawn on day one.