Mortgage Overpayment Calculator
Paying more than your required monthly mortgage payment can significantly reduce total interest and shorten your term. Most UK lenders allow 10% overpayments annually without penalty.
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A common mistake is assuming all extra payments go straight to reducing your balance. Some lenders apply overpayments as future payment credits rather than capital reductions – check your lender's policy.
A mortgage overpayment essentially earns you a guaranteed return equal to your mortgage rate. Enter your mortgage details below to see how much you could save.
Your Mortgage Details
Current Monthly Payment
£0
Based on your mortgage details
Overpayment Impact
Interest Saved
£0
By overpaying £0 total
Time Saved
0 months
Off your mortgage term
Original End Date
Oct 2026
New End Date
Oct 2026
Effective Return
0%
Return on your overpayments (via saved interest)
Comparison
Without Overpaying
Interest: £0
Total: £0
With Overpaying
Interest: £0
Total: £0
Before Overpaying
- • Check your Early Repayment Charge (ERC) terms
- • Most lenders allow 10% overpayment per year
- • Overpaying reduces balance, not monthly payment
- • Consider keeping an emergency fund first
What this means for your mortgage
Every £100 you overpay earns a guaranteed, tax-free return equal to your mortgage rate — typically 4–5% in 2026. That's better than most easy-access savings accounts after tax, with zero market risk. Even a £100/month overpayment on a £200k mortgage at 4.5% can knock 4+ years off the term and save £20k+ in interest.
But before piling in: keep an emergency fund (3–6 months of expenses), max your pension match at work, and check your lender's 10% annual overpayment cap to avoid Early Repayment Charges. If you're in a fixed deal with high ERCs, the Total Mortgage Calculator shows the full picture.
How Mortgage Overpayments Work
When you overpay your mortgage, 100% goes to reducing your outstanding balance. This means you pay interest on a smaller amount for the rest of your term—saving far more than the overpayment itself.
Why Overpayments Disproportionately Reduce Interest
Consider a £200,000 mortgage at 4.5% over 25 years:
No overpayment
£278,000
£78,000 interest
£100/month overpay
£244,000
£34,000 saved!
£200/month overpay
£222,000
£56,000 saved!
The "compound effect" works in your favour: paying down principal early means less interest accumulates for years to come. A £100 overpayment today saves more than a £100 overpayment in 10 years' time.
Early Repayment Charges (ERCs)
Important: Check your mortgage terms before making large overpayments. Most lenders have limits during fixed-rate periods.
Typical Limits
- • 10% of balance per year is common
- • Some lenders offer 20% or unlimited
- • Limits reset each year on anniversary
- • Fixed periods (2/5 year) have strictest limits
ERC Penalties
- • Typically 1-5% of excess overpayment
- • Charges reduce each year of fix
- • No ERCs on SVR or trackers usually
- • Check your mortgage offer document
Put a pound figure on the penalty with our erc calculator.
When Overpaying Makes Sense
Good reasons to overpay
- ✓ Mortgage rate higher than savings rates
- ✓ You have a solid emergency fund already
- ✓ You won't need the money for years
- ✓ You're a higher-rate taxpayer (savings interest taxed)
- ✓ You want to clear mortgage before retirement
- ✓ Peace of mind from reducing debt
Consider alternatives if...
- ✗ Savings rates beat your mortgage rate
- ✗ You have high-interest debt (credit cards)
- ✗ No emergency fund (aim for 3-6 months)
- ✗ You might need the money soon
- ✗ You're not maximising pension contributions
- ✗ Your employer matches pension contributions
Frequently Asked Questions
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