Bridging Loan Calculator: Work Out the Real Cost of Short-Term Finance

Use the bridging loan calculator above

Pop in your figures and the tool does the arithmetic for you: loan amount, monthly interest rate, term in months, and any fees. Within a second you will see the interest charged, the fees, and the total repayable at the end of the term. Read on for how the maths works, a full worked example, and the costs that catch people out.

What a bridging loan actually is

A bridging loan is short-term, secured finance designed to cover a gap, usually between buying a property and either selling another one or arranging a longer-term mortgage. Terms typically run from a few weeks up to 12 or sometimes 24 months. Because the lender takes on more risk over a short window and moves quickly, the cost is quoted as a monthly interest rate rather than the annual rate you would see on a standard mortgage.

People use bridging finance to buy at auction (where completion is often 28 days), to secure a property before their existing home sells, to fund a refurbishment that a mainstream lender will not touch, or to break a broken property chain. It is a tool for speed and flexibility, not for cheap borrowing. The whole point is that you have a clear, realistic way to pay it back, which lenders call your exit. That might be the sale of a property or a remortgage onto a normal product.

How bridging loan interest is calculated

Bridging loan interest is almost always charged monthly, not annually, and there are three common ways it is structured. Knowing which one you are being offered changes the cost considerably.

• Monthly serviced: you pay the interest each month, like an interest-only mortgage, and clear the capital at the end. Your monthly outgoing is real cash from your pocket.
• Retained (rolled up in advance): the lender calculates the full interest for the term and deducts it from the loan amount on day one, so you borrow more to cover it but pay nothing monthly.
• Rolled-up (compounded): interest is added to the balance each month and you settle everything at the end. Because each month's interest is charged on the growing balance, this costs slightly more than a flat calculation.

The plain-English formula for a simple monthly interest estimate is straightforward:

Monthly interest = loan amount × monthly rate.
Total interest = monthly interest × number of months.
Total cost = total interest + arrangement fee + exit fee + other fees.
Total to repay = loan amount + total cost.

So for a flat (non-compounded) bridge, if you borrow £200,000 at 0.85% a month for 9 months, the monthly interest is £200,000 × 0.0085 = £1,700, and over 9 months that is £15,300 before fees. If interest is rolled up and compounded, the calculation runs on the rising balance each month, which nudges the total a little higher. The bridging loan calculator handles both the flat and compounded versions so you can compare like for like.

Why the monthly rate matters so much

A monthly rate of 0.85% does not mean 0.85% a year. Roughly speaking, a 0.85% monthly rate is in the region of 10% a year once compounding is accounted for. That is why you should never compare a bridging rate against a mortgage rate as if they are the same number. A bridge is meant to be short, so the total pounds-and-pence cost stays manageable even though the annualised rate looks high.

Worked example: Priya buys at auction before her flat sells

Priya wins a buy-to-let at auction for £180,000 and must complete in 28 days. Her own flat is under offer but will not complete for around four months. She takes a bridging loan to cover the purchase and plans to repay it from the flat sale.

• Loan amount: £180,000
• Monthly interest rate: 0.79%
• Term: 5 months (she allows a buffer beyond the expected four)
• Arrangement fee: 2% of the loan = £3,600
• Exit fee: 1% of the loan = £1,800

Using the flat method:

• Monthly interest = £180,000 × 0.0079 = £1,422
• Total interest over 5 months = £1,422 × 5 = £7,110
• Fees = £3,600 + £1,800 = £5,400
• Total cost of borrowing = £7,110 + £5,400 = £12,510
• Total to repay = £180,000 + £12,510 = £192,510

If Priya's flat sells a month late and the bridge runs to 6 months, that one extra month adds another £1,422 in interest, taking the cost of borrowing to £13,932. This is the single biggest thing people underestimate: every extra month is real money, so always model a longer term than you expect to need.

Second example: a homeowner breaking a chain

Tom and Sarah have found their next home at £420,000 but their buyer pulled out at the last minute. They take a £250,000 bridge against their existing home at 0.72% a month for 4 months, with a 1.5% arrangement fee (£3,750) and no exit fee. Monthly interest is £250,000 × 0.0072 = £1,800. Over 4 months that is £7,200 of interest, plus £3,750 in fees, giving a total borrowing cost of £10,950. They repay the bridge in full when their existing home finally completes.

Fees and exit costs to factor in

The monthly rate is only part of the picture. A bridging loan calculator that only shows interest will flatter the deal. Build these into your numbers:

• Arrangement (facility) fee: usually 1% to 2% of the loan, often added to the balance rather than paid upfront.
• Exit fee: not every lender charges one, but where it exists it is commonly 1% of the loan or one month's interest.
• Valuation fee: the lender will want the security property valued, and you pay for it.
• Legal fees: you typically cover both your own and the lender's legal costs.
• Broker fee: many bridges are arranged through a specialist broker who charges a percentage or flat fee.
• Telegraphic transfer / admin fees: small but real charges at drawdown and redemption.

On a six-figure loan these can add several thousand pounds. Always ask for the total cost of credit in writing and check whether interest is serviced, retained or rolled up, because that decides whether you need monthly cash flow or just a bigger exit lump sum.

Loan to value and why it caps how much you can borrow

Bridging lenders lend against the value of the security property, expressed as a loan-to-value (LTV) percentage. Most cap residential bridging at around 70% to 75% LTV, and the gross loan (including any retained interest and fees) has to fit inside that ceiling. If you are buying a run-down property to refurbish, the lender may lend against the current value rather than the post-works value unless it is a specialist refurbishment product. Working out your LTV first tells you whether the deal is even possible before you fall in love with a property. Our loan to value calculator helps you check that ratio quickly, and the mortgage calculator is useful for modelling the longer-term finance you might exit onto.

When bridging finance makes sense, and when it does not

Bridging works well when speed genuinely unlocks value: an auction purchase, a below-market opportunity, a chain break that would otherwise collapse a sale, or a refurbishment that turns an unmortgageable property into a mortgageable one. In those cases the cost of the bridge is small next to the gain or the deal saved.

It works badly as a substitute for a mortgage you simply cannot get, or when your exit is vague. If your plan to repay is "I'll sell, probably, at some point," you are exposed. Property sales slip, mortgage offers fall through, and every month of delay piles on interest. Before you commit, write down your exit, the date you expect it, and what happens if it is three months late. Then check the cost at that longer term.

If you are bridging into a buy-to-let, model the onward finance too. A landlord exiting onto a buy-to-let mortgage should sanity-check affordability with a buy to let mortgage calculator, and anyone refinancing an existing property to release a deposit can use a remortgage calculator to see whether that is cheaper than a bridge.

Common mistakes people make with bridging loans

• Comparing the monthly rate to a mortgage rate. A 0.85% monthly rate is roughly 10% a year, not 0.85% a year. Convert before you judge it.
• Forgetting the fees. Arrangement, exit, valuation, legal and broker fees can add 3% to 5% of the loan. The interest alone understates the true cost.
• Underestimating the term. Bridges almost always run longer than planned. Always price in a month or two of buffer.
• Ignoring how interest is charged. Retained interest reduces the cash you receive on day one; rolled-up interest compounds. Both change what you actually pocket and repay.
• No clear exit. Lenders care most about how you will repay. If your sale or remortgage is uncertain, the risk is yours, and so is the bill if it drifts.
• Borrowing the gross when you only need the net. If fees and interest are added to the loan, you are paying interest on those amounts too. Keep the loan as lean as the deal allows.

You can compare a bridge against ordinary borrowing using our general loan calculator, which is handy when a personal or secured loan might do the job for a smaller, non-property gap.

How accurate is this calculator?

The tool gives a realistic working estimate based on the figures you enter. It is not a quote. Actual costs depend on the lender's underwriting, the valuation, your exit, the security property and your circumstances. Bridging is a specialist, often unregulated, area of lending, so always take advice from a qualified broker or adviser and read the full credit agreement before committing.

These figures are estimates for guidance only and are not personal financial advice. Always confirm the exact terms with your lender or a qualified adviser before borrowing.

For background on how bridging loans work and what to watch for, see MoneyHelper's guide to bridging loans. If you are dealing with a lender or broker, you can check they are authorised on the Financial Conduct Authority register.

Related calculators

Once you have a feel for the bridging cost, plan the wider picture with our mortgage calculator for the long-term finance you might exit onto, the loan to value calculator to check how much you can borrow against the property, and the remortgage calculator if refinancing is part of your repayment plan.