A HELOC lets you borrow up to 85% of your home's value minus your mortgage balance.
What this calculator does
HELOCs have variable rates — typically prime + 0–2%.
When to use this calculator
Reach for this tool whenever a financial decision hinges on this type of calculation. Small differences in rate or term become large differences in total cost or return over multi-year horizons — differences that only become visible when you run the actual numbers.
Common mistakes
A frequent error is using annual rates where monthly rates are required (or vice versa). Simply dividing an annual rate by 12 is only an approximation — the correct conversion for compound calculations uses the (1 + r)^(1/12) − 1 formula.
Real-world scenarios
A first-time buyer models three scenarios before making an offer: 10%, 15%, and 20% deposit on a £280,000 property. The calculator shows exactly how the monthly payment and total interest cost change with each deposit level, making the decision visible rather than speculative.
Frequently asked questions
How much HELOC can I get?
Up to 85% of your home value minus your mortgage balance. On a $400K home with $200K mortgage: