A HELOC charges interest on the drawn balance, not the full facility limit, which means the monthly payment depends on how much has been drawn and when. This calculator models both scenarios: drawing the full amount on day one and drawing gradually over the draw period. During the draw period, payments are interest-only on the drawn balance. When the draw period ends, the balance converts to capital-plus-interest repayments over the remaining term. Enter the amount, rate, and term to see the monthly payment, total interest, and the saving from staged drawdown. All figures are illustrative only and do not represent a specific product offer.
At a Glance
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Enter the amount you plan to borrow, the illustrative interest rate, the draw period length, and the total term. The calculator shows two scenarios side by side.
Scenario A shows the cost if the full amount is drawn on day one, with interest-only payments during the draw period and capital-plus-interest during the repayment period. Scenario B shows how the interest-only payment builds if the amount is drawn gradually, with the same capital-plus-interest repayment period afterwards. Both scenarios reflect how UK HELOC products work: interest-only during the draw period, capital-plus-interest once the draw period ends.
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The interest saving from drawing gradually can be significant. On a £50,000 facility at 8.5% over 20 years, drawing gradually over a five-year draw period saves approximately £10,400 in total interest compared with drawing the full amount on day one.
The saving comes entirely from the draw period. A borrower who draws everything on day one pays interest on the full £50,000 for the entire draw period. A borrower who draws gradually pays interest on a much smaller average balance during those same years. The repayment period after the draw ends is identical for both scenarios.
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Monthly payments increase when the draw period ends and the balance converts to capital-plus-interest repayments.
During the draw period, payments are interest-only on the drawn balance. When the draw period ends, the full outstanding balance converts to capital-plus-interest over the remaining term, and the monthly payment increases. On a fully drawn £50,000 facility at 8.5%, the payment increases from approximately £354 per month (interest only) to approximately £492 per month (capital plus interest over 15 years). Borrowers should budget for the repayment-period payment, not the draw-period payment. All figures are illustrative.
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This calculator excludes fees. Lender fees and broker fees add to the total cost and should be factored into any product comparison.
The figures shown are interest and capital repayment only. Product fees, arrangement fees, and broker fees are not included. These can be significant for HELOC products and will increase the total cost beyond what the calculator shows. The guide to HELOC fees and costs covers the full fee breakdown.
HELOC repayment calculator
Illustrative figures only. Excludes fees. Not a quote or offer.
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interest saved by drawing gradually over the draw period
Payment profile: gradual draw (by year)
All figures are illustrative and simplified. Interest-only payments during the draw period, capital-plus-interest during the repayment period, reflecting UK HELOC product structure. Gradual draw assumes equal monthly draws spread evenly over the draw period. Fees (lender product fee, arrangement fee, and broker fee) are excluded and would increase the total cost. This calculator does not constitute a quote, offer, or financial advice.
About this tool
What it calculates
Monthly payments and total interest under two drawdown patterns
The calculator models the same amount borrowed under two scenarios: drawing the full amount on day one and drawing gradually over the draw period. Both use interest-only payments during the draw period and capital-plus-interest during the repayment period, reflecting how UK HELOC products work. The payment profile chart shows how the interest-only payment builds during the draw period under the gradual draw scenario, then jumps to the capital-plus-interest level when the repayment period begins.
What it does not include
Fees, valuation costs, and product-specific terms
The figures shown are interest and capital repayment only. Lender product fees, arrangement fees, broker fees, and any valuation or legal costs are excluded. These can be significant for HELOC products and will increase the total cost beyond what the calculator shows. The guide to HELOC fees and costs itemises every fee category.
How to use this calculator
Set the amount you plan to borrow
Move the slider or note the figure. This represents the total HELOC facility you are considering. UK HELOC facilities typically range from £5,000 to £500,000, though the amount available depends on property equity and affordability. The guide to understanding LTV for HELOCs explains how the maximum is calculated.
Set the illustrative interest rate
The rate depends on the combined LTV, credit profile, and draw period length. As a guide, rates typically range from 6.5% at lower LTV tiers to 13% or more at higher tiers. The guide to HELOC rates in the UK includes illustrative rate bands by LTV. The rate you are offered will be confirmed during the application process.
Set the draw period and total term
The draw period is the window during which you can draw, repay, and redraw funds (typically two to five years in the UK). During this phase, payments are interest-only on the drawn balance. The total term is the full period from start to final repayment (typically five to thirty years). When the draw period ends, the balance converts to capital-plus-interest over the remaining term.
Read the two scenarios and the interest saving
The left panel shows what happens if the full amount is drawn on day one. The right panel shows what happens if the same amount is drawn gradually over the draw period. The saving figure shows how much less interest is paid under the gradual draw scenario. The payment profile chart shows how the interest-only payment builds during the draw period and jumps to the capital-plus-interest level in the repayment period.
Understanding the results
The “drawn all at once” panel shows two payment levels. During the draw period, the borrower pays interest only on the full amount: on £50,000 at 8.5%, that is approximately £354 per month. When the draw period ends, the balance converts to capital-plus-interest repayments over the remaining term, and the payment increases to approximately £492 per month over 15 years. This two-phase structure is how UK HELOC products work for any borrower, whether they draw all at once or gradually.
The “drawn gradually” panel shows a different draw-period pattern but the same repayment period. The interest-only payment in year one is low because only a small portion of the total has been drawn. It builds each month as more is drawn, reaching the same £354 by the end of the draw period (because the full amount has been drawn by that point). When the draw period ends, the repayment-period payment is identical to the full-draw scenario: approximately £492 per month. The interest saving comes entirely from carrying a lower average balance during the draw period, when payments are interest-only.
The payment profile chart makes this pattern visible. During the draw period (shown in navy), the interest-only payment increases each year as more is drawn. When the repayment period begins (shown in teal), the payment jumps to the capital-plus-interest level and stays flat for the rest of the term. Borrowers should budget for the repayment-period payment, not the draw-period payment, because that is the long-term commitment and the level at which affordability is assessed. The guide to what is a HELOC covers the full two-phase lifecycle.
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Checking won’t harm your credit scoreFrequently asked questions
What happens to the monthly payment when the draw period ends?
During the draw period, payments are interest-only on the drawn balance. When the draw period ends, the outstanding balance converts to capital-plus-interest repayments over the remaining term. This means monthly payments increase at the transition point. On a fully drawn £50,000 facility at 8.5% transitioning from a 5-year draw to a 15-year repayment period, the payment increases from approximately £354 per month to approximately £492 per month, an increase of around 39%. All figures are illustrative.
The provider assesses affordability at the repayment-period payment level before the facility is set up, so the borrower must be able to afford the higher post-transition payment from the outset. This transition is smaller than the equivalent on a US HELOC (where the longer 10-year draw period produces a sharper increase), but it is still a real increase that borrowers should plan for. The guide to HELOC risks explained covers the transition in detail.
Borrowers can make voluntary overpayments during the draw period to reduce the balance before the transition. This lowers the repayment-period payment because the capital-plus-interest calculation is based on the balance outstanding when the draw period ends. There are no early repayment charges on UK HELOC products at the time of writing.
Does the calculator account for fees?
No. The figures shown are interest and capital repayment only. HELOC fees, including the lender product fee (typically 2.0% to 2.6% of the facility amount, capped), the lender arrangement fee (typically 6.7% to 7.8%, capped at £3,000), and any broker fee (typically 5% to over 10% of the facility amount), are excluded. These fees can be significant and should be factored into any cost comparison between products.
If fees are added to the facility balance rather than paid upfront, the borrower pays interest on the fee amount over the remaining term. As an illustrative example, adding £5,000 of fees to the balance at 8.5% over 20 years adds approximately £5,400 in interest on the fees alone. The guide to HELOC fees and costs covers the impact of adding fees to the balance.
For a complete cost comparison that includes fees, the APRC (annual percentage rate of charge) is the most reliable metric. The APRC includes all lender fees alongside the interest rate. However, broker fees may not be captured in the APRC, so the total cost across different brokers should be compared separately. The guide to APR on secured loans explains how APRC works.
How accurate is the gradual draw model?
The calculator models equal monthly draws spread evenly over the draw period. In practice, most borrowers do not draw in this pattern. A homeowner funding a phased extension draws at each project stage (for example, five draws over eight months). A parent paying school fees draws termly (three draws per year). The actual interest saving depends on the specific timing and amounts of each draw.
As a general guide, the equal-monthly-draw model provides a reasonable middle estimate. If more of the total is drawn earlier in the draw period, the actual interest saving will be smaller than the calculator shows, because the average balance is closer to the full amount for most of the period. If more is drawn later, the saving will be larger. The model is most accurate for borrowers who expect their spending to be spread relatively evenly across the draw period.
The “drawn all at once” scenario is precise: it shows interest-only on the full amount during the draw period followed by a standard capital-plus-interest amortisation during the repayment period. This figure is useful for comparison with standard second charge mortgage products. The guide to home equity loan vs HELOC covers the full comparison between the two product structures.
What rate should I use in the calculator?
The rate depends on the borrower’s circumstances, particularly the combined LTV and credit profile. As a starting point, rates below 8% are typically available at combined LTV below 65% with clean credit. Rates of 8% to 10% are common at 65% to 80% LTV. Rates above 10% are more typical at higher LTV tiers or for borrowers with adverse credit. The guide to HELOC rates in the UK includes illustrative rate bands.
Most UK HELOCs carry variable rates, typically linked to the Bank of England base rate or a similar reference rate, which means the rate can change during the term. The calculator uses a fixed rate for simplicity. If the reference rate rises, the actual monthly payment and total interest will be higher than the calculator shows. If it falls, they will be lower. Borrowers who are concerned about rate variability should consider whether a fixed-rate option is available. The guide to fixed vs variable rate HELOCs covers this decision.
The rate entered into the calculator does not need to be exact. Trying several rates (for example, 7%, 8.5%, and 10%) shows how sensitive the monthly payment and total interest are to the rate, which helps with planning even before the actual rate is confirmed during the application process.
Can I use this calculator for a standard secured loan comparison?
Partially. The “drawn all at once” panel shows a HELOC where the full amount is drawn on day one, which means interest-only during the draw period followed by capital-plus-interest during the repayment period. A standard secured loan works differently: capital-plus-interest from day one with no interest-only phase. To get a true standard loan comparison figure, set the draw period to its minimum (2 years) and compare the repayment-period payment, which is the capital-plus-interest figure.
The “drawn gradually” panel is HELOC-specific and shows the benefit of the revolving drawdown structure. If you are comparing a HELOC with a standard loan, the saving figure shows how much less interest the HELOC would cost if you draw gradually, which is the structural advantage that makes a HELOC worth considering for phased spending. If you plan to draw the full amount on day one, the main comparison point is the total interest over the full term, factoring in the interest-only draw period that a HELOC includes.
For a more detailed side-by-side comparison, the HELOC vs lump sum comparator is specifically designed for this. The guide to HELOC vs remortgage covers the comparison with remortgaging, including the hidden cost of losing a favourable existing mortgage rate.
Squaring Up
The HELOC repayment calculator shows two sides of the same borrowing amount: the cost if drawn all at once and the cost if drawn gradually over the draw period. Both scenarios use interest-only payments during the draw period and capital-plus-interest during the repayment period, reflecting how UK HELOC products work. The interest saving from gradual draws comes from carrying a lower average balance during the interest-only phase, when every pound of balance reduction directly reduces the monthly payment.
The calculator excludes fees, which are a material part of the total cost for HELOC products. For a complete picture, the interest figures from this calculator should be combined with the fee estimates from the HELOC fees and costs guide. The rate used is illustrative and most UK HELOCs carry variable rates, so the actual cost will depend on how the reference rate moves over the term.
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Checking won’t harm your credit score Check eligibilityThis calculator is for illustrative purposes only and does not constitute financial advice, a quote, or an offer. Your home may be at risk if you do not keep up repayments on a mortgage or other debt secured against it. The figures shown exclude fees (lender product fee, arrangement fee, and broker fee) which form a material part of the total cost. Interest rates are illustrative; most UK HELOCs carry variable rates that can change during the term. Actual payments and total costs depend on the specific product, rate, fees, and individual circumstances.
