Negative Equity Calculator
Last updated: 27 June 2026
Reviewed by Gavin Meiring, Lead research and primary author · Doctoral Candidate (Corporate Governance) · Research and drafting assisted by AI
- Negative equity swept the UK in the early 1990s, when house prices fell by around a fifth after the late-1980s boom, leaving hundreds of thousands of borrowers owing more than their homes were worth.
- Japan's experience was far longer: after its property bubble burst in 1991, prices fell for more than a decade, keeping millions of homeowners in negative equity for years.
- The term gained wide currency in Britain after lenders like Northern Rock offered 125% mortgages, which put borrowers in negative equity from day one.
Negative Equity Calculator
A negative equity calculator shows whether your outstanding mortgage is greater than the current value of your property. It is used by homeowners who want to understand their financial position, particularly in falling property markets or during early years of repayment when little capital has been paid down.
How to Use the Negative Equity Calculator
- Enter the current estimated market value of your property.
- Enter the outstanding balance remaining on your mortgage.
- The calculator subtracts the outstanding mortgage from the property value to give your equity position.
- A positive result indicates equity. A negative result indicates negative equity, showing how much your debt exceeds your property's value.
- Review your current LTV ratio alongside the equity figure to understand your position relative to typical lender thresholds.
The Formula
Equity = Current Property Value - Outstanding Mortgage Balance
If this figure is negative, you are in negative equity. The negative equity amount is the absolute value of the difference.
Negative Equity Amount = Outstanding Mortgage - Current Property Value (when mortgage exceeds value)
LTV in this case = (Outstanding Mortgage / Current Property Value) x 100, which will be above 100%.
Real-World Example
You bought a property for £250,000 with a 10% deposit of £25,000, so your original mortgage was £225,000. Property values in your area have since fallen by 12%.
Current property value = £250,000 x 0.88 = £220,000.
After two years of repayment, your outstanding mortgage balance is £218,000.
Equity = £220,000 - £218,000 = £2,000.
You are marginally in positive equity. However, if values had fallen 15% instead, your property value would be £212,500 and you would be in negative equity by £5,500.
What to Do If You Are in Negative Equity
Being in negative equity limits your options but does not necessarily require immediate action if you can continue meeting your repayments. You cannot typically remortgage to a new deal with a different lender when in negative equity, which may mean you are stuck on your existing lender's standard variable rate when your deal expires. Some lenders offer product transfers to existing customers in negative equity, though options are limited. Making overpayments when affordable is the most reliable way to reduce the gap. Waiting for property values to recover is a valid strategy if your financial position is otherwise stable. Selling is usually only advisable if you can bridge the shortfall yourself or negotiate an assisted sale with your lender.
Frequently Asked Questions
Is negative equity illegal or a breach of my mortgage terms? No. Negative equity is a financial condition, not a breach of contract. As long as you continue making your mortgage repayments on time, your lender cannot force you to sell or take additional action simply because the property has fallen in value.
Can I remortgage if I am in negative equity? Remortgaging to a new lender is generally not possible in negative equity. However, your existing lender may offer a product transfer, allowing you to switch to a new rate without a new affordability assessment. Contact your lender directly to explore options.
How long does negative equity last? It depends on how far values have fallen and how quickly they recover. Recovery from the 2008 financial crisis took around 5-10 years in many UK regions. Regular overpayments can reduce negative equity faster than waiting for property prices to rise.
Does negative equity affect my credit score? Not directly. Negative equity is not recorded on your credit file. However, missed mortgage payments resulting from financial stress associated with negative equity will damage your credit score, so maintaining repayments is critical.
The value decline that puts the mortgage under water
The example above stops at a 12% fall, where £2,000 of equity remains. The full picture across the range of falls is set out below, using the same purchase of £250,000 with a £25,000 deposit, an original mortgage of £225,000 and an outstanding balance of £218,000 after two years of repayment.
| Fall in value | Property value | Equity | LTV at that value |
|---|---|---|---|
| 5% | £237,500 | £19,500 | 91.79% |
| 8% | £230,000 | £12,000 | 94.78% |
| 10% | £225,000 | £7,000 | 96.89% |
| 12% | £220,000 | £2,000 | 99.09% |
| 12.80% | £218,000 | £0 | 100.00% |
| 15% | £212,500 | minus £5,500 | 102.59% |
| 20% | £200,000 | minus £18,000 | 109.00% |
The break-even sits at 12.80%, and it comes from the balance rather than from the original loan. Divide the balance by the purchase price, £218,000 by £250,000, which gives 0.8720, and the remaining 12.80% is the amount the value can fall before the two are equal. The £7,000 of principal repaid over the two years is what moved the break-even down from the 10.00% that the deposit alone would give.
What an overpayment does to the break-even point
An overpayment attacks the same number from the other side. Every pound taken off the balance lowers the value at which the mortgage and the property meet, and the effect compounds because the overpayment also removes the interest that pound would have carried.
| Payment on top of the mortgage | Run for | Taken off the balance | New balance | Fall in value that would wipe out the equity |
|---|---|---|---|---|
| None | £0 | £218,000 | 12.80% | |
| £200 a month | 12 months | £2,400 | £215,600 | 13.76% |
| £200 a month | 24 months | £4,800 | £213,200 | 14.72% |
| £200 a month | 36 months | £7,200 | £210,800 | 15.68% |
The table counts only the money paid, so it understates the result. An overpayment also trims the interest charged on the balance, which means the real balance after 24 months is a little below £213,200. The direction of the error is in the borrower's favour, which is the safer way for an estimate to be wrong.
What the last big fall looked like in real numbers
The Bank of England measured the 2008 episode in a Quarterly Bulletin article in 2009. Nominal house prices fell by around 20% between the autumn of 2007 and the spring of 2009, the largest fall in nominal prices on record, and the Bank published three separate estimates of what that did to mortgage holders.
| Measure | Estimate |
|---|---|
| Fall in nominal house prices, autumn 2007 to spring 2009 | around 20% |
| Share of UK owner-occupier mortgagors in negative equity, 2009 Q1 | 7% to 11% |
| Households that represents | 700,000 to 1.1 million |
| Estimate from the Council of Mortgage Lenders, end of 2008 | 900,000 households |
| Estimate using lenders' own LTV data | around 10%, about 1 million households |
| Estimate from the Financial Services Authority, 2009 Q1 | around 11%, about 1.1 million households |
| Buy-to-let mortgages also in negative equity, 2009 Q1 | around 200,000 |
| Mortgagors with an LTV below 75% | over 75% |
The three estimates differ because they measure different things. The household survey route returned the lowest figure, and the Bank noted that survey respondents tend to overstate the value of their own homes, which pushes the measured incidence down. The two routes that work from actual lending data landed close to each other, at around 10% and around 11%.
The same Bank work records the survey reading for negative equity rising from around 1% in September 2007 to around 5% in 2009. That is the honest shape of the risk: a large fall in prices moved a small minority of mortgagors into negative equity, and for most of those households the shortfall was modest. The majority of mortgage holders carried substantial equity throughout.
Applying a 20% fall to the worked example
Run the 2008 fall through the £250,000 purchase. The value becomes £200,000, the balance stays at £218,000, and the shortfall is £18,000 at an LTV of 109.00%.
Two recovery thresholds follow from those figures, and both are useful for judging how far away a way out is.
The first is the point at which the balance and the value are equal again. That needs a rise of 9.00%, because £218,000 divided by £200,000 is 1.09. In cash terms the property has to regain £18,000.
The second is the point at which the loan becomes remortgageable at 90% LTV, which is the top of the range most mainstream lenders work to. The value has to reach £242,222.22, because £218,000 divided by 0.90 gives that figure, and that is a rise of 21.11% from £200,000. The gap between the two thresholds, 9.00% against 21.11%, is why a homeowner can be back above water and still unable to move to a new lender.
Method and what the calculation does not include
The measure needs one property value and one mortgage balance. Three points about the inputs are worth stating.
The value is an estimate, and the estimate that matters is a lender's. An owner's view of what the property is worth and a valuer's opinion can differ, and the LTV a lender will act on uses the valuation rather than the asking price or a neighbour's sale.
The balance should be the redemption figure, not the statement balance. Interest accrued to the day of settlement, any early repayment charge and any fee added to the loan all belong in the number, and leaving them out flatters the position.
The calculation covers the first charge on the property and nothing else. A second charge, a Help to Buy equity loan, a shared ownership share or a loan secured on another property all reduce what the owner actually holds, and none of them appears in a single-balance comparison. An equity loan is not a mortgage, but it is still a claim on the same asset.
One further limitation follows from the shape of the sum. Subtracting debts from values produces a figure that moves with both sides at once, and a property is the least liquid thing most households own. The number says where the owner stands on the day it is calculated, and it says nothing about how quickly that position can be changed.
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