Second Mortgage Affordability Calculator
Your Borrowing Capacity
Available Equity-
Max Based on LTV-
Max Based on Income (4.5×)-
Est. Monthly Payment-
Maximum You Could Borrow-
Borrowing Capacity by Property Value & Equity
| Property | Mortgage | Equity | Max 2nd (80% LTV) |
|---|---|---|---|
| £200,000 | £120,000 | £80,000 | £40,000 |
| £300,000 | £180,000 | £120,000 | £60,000 |
| £400,000 | £200,000 | £200,000 | £120,000 |
| £500,000 | £250,000 | £250,000 | £150,000 |
Maximum = (Property × LTV) minus existing mortgage. Income affordability also applies.
Affordability Factors
Income Multiple
3.5–4.5×
Max Combined LTV
75–85%
Min Property
£70,000
Stress Test
+3% above SVR
Min Equity
15–25%
Proof Required
3 months payslips
How to Use This Calculator
1
Enter gross annual income
Input total annual salary before tax. Joint applications may combine incomes.
2
Enter property value
Input your property’s current market value to determine available equity.
3
Enter existing mortgage
Input outstanding first mortgage balance for LTV and equity calculations.
4
Add monthly commitments
Include credit cards, car finance, personal loans that affect affordability.
5
Review borrowing capacity
The lower of LTV-based and income-based limits determines your maximum.
Frequently Asked Questions
How much can I borrow on a second mortgage?
Most lenders use combined LTV of 75-85% and income multiple of 3.5-4.5×. Your maximum is the lower of available equity and income affordability.
What income do I need?
No fixed minimum, but you need sufficient disposable income after commitments. Lenders stress-test at +3% above the actual rate.
Does my existing mortgage rate matter?
Yes — total monthly housing costs including both mortgages must be affordable. A low first mortgage rate helps.
Can self-employed people apply?
Yes, with 2-3 years of accounts or SA302 tax calculations. Lenders use average net profit.
What credit score is needed?
Good credit unlocks best rates. Specialist lenders accept CCJs and defaults at higher rates and lower LTV limits.
Official Sources & References
Data verified against official UK government sources. Last checked April 2026.