To calculate a bridge loan, work out how much you need to borrow (usually the purchase price plus costs, minus any cash you are putting in), check it against the lender’s maximum loan-to-value, then add the monthly interest for the number of months you expect to borrow, plus arrangement, valuation, legal and exit fees. The total of interest and fees is the true cost of the bridge, and the amount you must repay on exit is the loan plus anything that has been rolled up.
A bridge loan (called a bridging loan in the UK) is short-term secured finance that covers a gap between two transactions, most often buying a new property before the sale of an existing one completes. This guide takes a methodical approach: what the numbers are, how to run them step by step, a worked example, and the repayment planning that decides whether a bridge is a sensible choice.
What Is a Bridge Loan and When Is It Used?
A bridge loan is a temporary loan secured on property, designed to be repaid in one lump sum from a known source of money, such as a house sale, a remortgage or the release of other funds. Terms are short, commonly a few months up to around 12 to 18 months, and the lender cares far more about how you will repay (your “exit”) than about monthly affordability.
Typical situations include:
- Chain breaks: buying your next home before your current one sells, so you do not lose the purchase.
- Auction purchases: auction buyers usually need to complete within a fixed, short period, often faster than a standard mortgage can be arranged.
- Unmortgageable properties: buying a property that needs work (no working kitchen or bathroom, for example) before a normal mortgage lender will accept it.
- Business and investment needs: short-term funding for a commercial purchase, refurbishment or a cash-flow gap while longer-term finance is arranged.
Because the loan is short and the lender relies on a single exit event, rates are higher than a standard residential mortgage. That is why calculating the full cost before you commit matters more here than with almost any other kind of borrowing.
Open and Closed Bridging: Why the Type Affects Your Numbers
There are two broad types, and they change how a lender looks at your case:
| Feature | Closed bridge | Open bridge |
|---|---|---|
| Exit date | Fixed and known (e.g. exchange of contracts has happened on your sale) | No fixed date; the exit is expected but not yet certain |
| Lender risk | Lower | Higher |
| Typical pricing | Often cheaper | Often more expensive |
| Best suited to | Sales that have exchanged, confirmed remortgages | Properties on the market without a buyer, refurbishment projects |
Bridging loans can also be first charge (the only loan on the property) or second charge (sitting behind an existing mortgage). Second charge loans usually cost more because the lender is paid after the first mortgage if things go wrong. In the UK, bridging secured on a home you or your family live in is generally regulated by the Financial Conduct Authority, while investment and commercial bridging usually is not, which affects the protections you have.
The Figures You Need Before You Calculate
Whether you use a spreadsheet or an online tool such as the bridge loan direct bridging loan calculator, the result is only as good as the inputs. Gather these first:
- Gross loan amount: the total you will borrow, including any fees and interest added to the loan.
- Property values: the value of the property being bought and of any property offered as additional security.
- Maximum loan-to-value (LTV): the percentage of the security value the lender will lend against. Many lenders cap this at somewhere around 70 to 75 percent, though it varies by lender and case.
- Monthly interest rate: bridging rates are quoted per month rather than per year.
- Interest method: serviced (paid monthly), retained (deducted upfront for an agreed period) or rolled up (added to the balance and repaid at the end).
- Fees: arrangement fee, valuation, both sides’ legal costs, broker fee and any exit fee.
- Term: the number of months you realistically expect to need, plus a buffer.
Lenders look closely at your existing commitments and credit history too, so it is worth reviewing the common reasons lenders reject a loan application before you apply.
How to Calculate Your Bridge Loan: Step by Step
- Work out the funding gap. Purchase price plus stamp duty, legal costs and moving costs, minus the cash you have available.
- Check the LTV limit. Multiply the value of all security by the lender’s maximum LTV. If the funding gap is bigger than this, you need more deposit or more security.
- Choose the interest method. If interest is rolled up or retained, the lender includes it in the gross loan, which uses up part of your LTV allowance.
- Calculate monthly interest. Loan amount multiplied by the monthly rate. For rolled-up interest, many lenders compound monthly, so each month’s interest is charged on the growing balance.
- Add every fee. Arrangement fees are often a percentage of the loan; valuation and legal fees are fixed amounts that you should get quoted.
- Multiply by a realistic term. Use your expected term plus two or three months in case the sale is slower than planned.
- Compare the total cost with the benefit. If the bridge saves a purchase worth having, the cost may be justified; if it simply speeds things up slightly, it may not be.
A Worked Example (Illustrative Figures)
The numbers below are purely illustrative to show the method; they are not a quote, and your rate and fees will depend on the lender and your circumstances.
Suppose you are buying a home for £400,000 and your current home is under offer at around £300,000 with £100,000 left on the mortgage. You need to borrow £300,000 for six months, at an illustrative rate of 0.75% per month with interest rolled up, plus a 2% arrangement fee.
| Item | Calculation | Illustrative amount |
|---|---|---|
| Net loan | Amount needed for the purchase | £300,000 |
| Arrangement fee | 2% of £300,000 | £6,000 |
| Monthly interest (simple) | £300,000 × 0.75% | £2,250 |
| Interest over 6 months (simple) | £2,250 × 6 | £13,500 |
| Valuation and legal fees | Get quotes; varies widely | Fixed amounts |
| Approximate total cost | Interest + arrangement fee + other fees | £19,500 plus valuation and legal |
If interest compounds monthly, the six-month figure is slightly higher than the simple calculation. If the sale slips by three months, add another three months of interest, which is why the buffer in step six matters. A good calculator will show both the gross loan and the amount you need to repay on exit, so you can check that the sale proceeds will comfortably cover it.
Interest-Only, Retained and Rolled-Up Interest Compared
How you pay the interest affects both your monthly budget and the size of the debt at the end:
| Method | What you pay monthly | Effect at the end | Suits |
|---|---|---|---|
| Serviced | Interest each month | Repay the original loan only | Borrowers with steady income |
| Retained | Nothing (interest held back upfront) | Repay the gross loan | Short, predictable terms |
| Rolled up | Nothing | Repay loan plus accumulated interest | Borrowers without spare monthly income |
Serviced interest keeps the final repayment lowest, but you need the income to cover it alongside your existing mortgage. Rolled-up interest protects your monthly household finances but steadily eats into the equity you will have left after the sale.
Designing Your Repayment Strategy
The exit is the most important part of any bridge loan. Lenders will ask for evidence of it, and you should test it as hard as they do. The most common exit is the sale of your existing property; others include a remortgage onto a standard mortgage once a property is habitable, or the release of funds from investments or a business transaction.
Build a backup plan before you sign. Ask yourself what happens if the buyer pulls out, if the sale price falls by ten percent, or if a remortgage valuation comes in low. Options might include reducing the asking price, extending the loan (usually at a cost), or refinancing onto a longer-term product. Planning for these scenarios is what turns a risky bridge into a seamless transition from one property or project to the next.
Common Mistakes to Avoid
- Comparing only the monthly rate and ignoring arrangement and exit fees.
- Assuming the sale will complete on time with no buffer in the term.
- Over-borrowing so that rolled-up interest leaves too little equity after the sale.
- Not checking whether the loan is regulated and what protection that gives you.
- Leaving the exit plan vague; lenders and you both need it in writing.
Is a Bridge Loan Right for You?
A bridge loan makes sense when the cost is clearly smaller than what it protects, such as a home you would otherwise lose or an auction property bought at a good price. It is harder to justify when the exit is uncertain or the margin between your sale proceeds and the repayment is thin. Taking independent advice is wise; for context on why outside views help with financial decisions, see how independent analysis is helping investors navigate today’s financial landscape. If you are planning to build rather than buy, our guide to self-build mortgages covers an alternative route to funding.
Bridging loans are secured on property, and your home may be repossessed if you do not keep up repayments. Speak to a qualified mortgage adviser or broker before committing, and read every fee in the offer document. You can find more guides in our Finance category.
Frequently Asked Questions
How do you calculate interest on a bridge loan?
Multiply the loan amount by the monthly interest rate to get one month’s interest, then multiply by the number of months you expect to borrow. If interest is rolled up and compounded, each month’s interest is charged on the new balance, so the total is slightly higher. Always add fees to get the full cost.
How much can I borrow with a bridging loan?
It depends mainly on the value of the security and the lender’s maximum loan-to-value. Many lenders cap total borrowing at around 70 to 75 percent of the security value, and rolled-up interest and fees count towards that limit.
What fees come with a bridge loan?
Expect an arrangement fee, a valuation fee, legal fees for you and the lender, and possibly a broker fee and an exit fee. Ask for a full breakdown so you can compare offers on total cost rather than headline rate.
How long can a bridge loan last?
Most bridging loans run for a few months up to around 12 to 18 months. Lenders expect repayment from a defined exit, so the term should match a realistic timeline for your sale or refinance with some margin.
What happens if my house does not sell in time?
You may be able to extend the loan, usually at extra cost, or refinance onto another product. If neither is possible, the lender can take action against the security, so a backup plan and an early conversation with the lender are essential.
Is a bridging loan better than a standard mortgage?
Not usually for long-term borrowing, as bridging rates are much higher. It is a short-term tool for specific gaps, and a standard mortgage is normally the cheaper option once the short-term need has passed.
Bottom Line on Calculating a Bridge Loan
Run the full numbers before you apply: the gross loan, the LTV, interest for a realistic term plus a buffer, and every fee. Then stress-test your exit. If the sale proceeds still cover the repayment comfortably when the timeline slips and the price dips, a bridge loan can do exactly what it is meant to do.
