Use this guarantor mortgage calculator to see how much more you could borrow if a parent or relative acts as your guarantor. It compares what you could borrow on your own income with what you could borrow when the lender also counts your guarantor’s spare income, and shows the monthly payment.
Borrowing with a guarantor
- You could borrow alone
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- With a guarantor
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- Mortgage you need
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- Monthly payment
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In the example, you earn £32,000 and want to buy a £220,000 home with a £5,000 deposit. On your own you could borrow about £144,000. With a guarantor whose spare income is £15,000, that rises to £211,500, close to the £215,000 you need. The payment would be £1,256.87 a month at 5%.
How to use the guarantor mortgage calculator
- Enter the price and your deposit.
- Enter your income before tax.
- Enter the guarantor’s spare income: what is left after their own mortgage, bills and debts as the lender sees it.
- Enter the rate and term.
How guarantor mortgages work
A guarantor agrees to cover your mortgage payments if you cannot. In return, the lender lets you borrow more, or with a smaller deposit, than you could alone. Some modern schemes do not use income at all: instead, a family member puts savings in a linked account, or the guarantor offers part of their own home as security.
- Income-based: the lender adds some of the guarantor’s income to yours.
- Savings-based (family springboard): family deposit 10% in a savings account for a set period.
- Security-based: a charge over the guarantor’s home.
- Joint borrower sole proprietor: the family member is on the mortgage but not the deeds.
Guarantor mortgage calculator examples
| Your income | Alone (4.5x) | With £10,000 guarantor income | With £20,000 |
|---|---|---|---|
| £22,000 | £99,000 | £144,000 | £189,000 |
| £28,000 | £126,000 | £171,000 | £216,000 |
| £32,000 | £144,000 | £189,000 | £234,000 |
| £40,000 | £180,000 | £225,000 | £270,000 |
Risks for the guarantor
The guarantor is legally responsible if you miss payments, which can affect their credit and, with security-based schemes, their home. They should take independent legal advice before signing. Many deals let the guarantor be released once you have paid the loan down or your income rises.
Related calculators
Work out the deposit you need with the mortgage deposit calculator, or consider buying a share with the shared ownership mortgage calculator.
Alternatives to a guarantor
If no one can act as a guarantor, consider a gifted deposit, a 95% mortgage, a longer term, buying with a friend or partner, or shared ownership. Some lenders now offer higher income multiples for first-time buyers. Compare monthly payments for each option before you decide, and use the guarantor mortgage calculator to see how close you are on your own income.
Frequently asked questions
Who can be a guarantor?
Usually a parent, grandparent or close relative who owns their home or has strong income, and who meets the lender’s age limits.
Can I get a 100% mortgage with a guarantor?
Some lenders offer 100% or close to it with a guarantor or family-backed scheme.
Does the guarantor go on the deeds?
Not usually. With a joint borrower sole proprietor mortgage they are on the loan but not the deeds.
How long does the guarantee last?
Until you have paid the loan down to an agreed level, or for a set number of years, depending on the scheme.
About this calculator
This guarantor mortgage calculator uses income multiples of 4.5 as a guide, checked against lender information and MoneyHelper on 9 November 2026. Results are estimates.