HELOC calculator: estimate your home equity line of credit limit, monthly interest-only and repay payments, and total cost. Free, editable rates, no signup.
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HELOC calculator: estimate your home equity line of credit limit, monthly interest-only and repay payments, and total cost. Free, editable rates, no signup.
Amortizing payment is 61% higher than the interest-only $270.83.
Transparent methodology
How this calculator works
Reviewed August 2026 · BoringToolsKit Editorial Team
BoringToolsKit. “HELOC Calculator.” boringtoolskit.com/heloc-calculator/ (reviewed August 2026). Free to reference in articles, syllabi, and answer posts with a link.
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Worked example: the payment jump at redraw
Take a $50,000 HELOC at 6.50% APR with a 10-year draw period and a 20-year total term. During the 10-year draw the payment is interest only: 50,000 x 0.065 / 12 = $270.83 per month, and 120 payments of that totals $32,500 in interest with the balance untouched.
After the draw ends, the remaining $50,000 must amortize over 180 months at a monthly rate of 0.065/12 = 0.0054167. The annuity formula P = L x r / (1 - (1 + r)^-180) gives 50,000 x 0.0054167 / (1 - 1.0054167^-180) = 270.83 / 0.6218 = $435.55 per month. That is a 61% jump from $270.83, and it is the single most common budget surprise with HELOCs.
Over the 180-month repayment phase you pay $435.55 x 180 = $78,399.66 total, or $28,399.66 in interest on top of the $32,500 from the draw phase. Total interest across both phases: about $60,900 on a $50,000 line. The calculator shows both payments side by side so you can see the jump before the lender does.
Where real HELOCs differ from this model
Most HELOCs use variable rates tied to the prime rate plus a margin. At prime of 7.50% with a 1.00% margin, 8.50% on $50,000 costs $354.17 per month interest only versus $270.83 at 6.50%: a $83.34 monthly swing. A 1% rate move during a 10-year draw period is realistic, so treat the payment shown as a snapshot, not a guarantee.
The amortization here starts from your full draw amount. In practice the payment is recalculated on whatever balance you actually owe when the draw ends. Drawing $20,000 of the $50,000 line and repaying $15,000 during the draw period leaves $5,000 to amortize, cutting the repayment-phase payment to roughly $43.55 at 6.50%.
Lenders also add costs this calculator ignores: annual fees of $50 to $85, inactivity fees after 12 to 24 months of no draws, early-closure penalties of $350 to $500 if you close within 3 years, and appraisals of $300 to $600 at origination. Some contracts require a minimum draw of $100 to $500 at closing. Check your agreement for all four before sizing the line, since fees can erase the rate advantage a HELOC has over a cash-out refinance.
