Free calculator
Flip profit calculator
Will your flip make money? Enter the purchase price, the refurb with a contingency on top, your buying, selling and finance costs, and the expected sale price, and this calculator gives you the total costs, the profit in pounds and the margin as a percentage of GDV.
Margin on GDV is the figure experienced flippers judge a deal by, because it measures the cushion between everything the project costs and what the finished property sells for. Common practice treats a margin below about 15% of GDV as leaving little room for error: one down-valuation, one overrun or one slow month of viewings and the profit is gone.
Flip profit calculator
Common practice treats a margin below about 15% of GDV as leaving little room for error. Benchmark the refurb line against the refurb cost data by region, and see what deal analysis shows for how often deals stack at asking price.
How the calculation works
Total costs are the purchase price, plus the refurb, plus a contingency taken as a percentage of the refurb, plus buying costs, selling costs and finance costs. Profit is the expected sale price, the GDV, minus those total costs. Margin on GDV divides the profit by the GDV rather than by the costs, which is deliberately the harsher measure: it asks what share of the end value you keep, which is how lenders and experienced buyers frame the risk.
The contingency defaults to 15% of the refurb because refurbs overrun and surveys miss things. Spending the contingency is not failure; the failure is the appraisal that never budgeted it.
Worked example: buy at £150,000, sell at £240,000
A £30,000 refurb carries a 15% contingency of £4,500. Buying costs are £6,000, selling costs £4,000 and finance £8,000. Total costs: £202,500. Sell at a GDV of £240,000 and the profit is £37,500, a 15.6% margin on GDV.
That clears the common 15% line, but only just. A £15,000 down-valuation to £225,000 drops the margin to 10.0%, which is why the GDV deserves more scrutiny than any other number on this page: price it from sold comparables, not from the best asking price on the street.
What this calculator does not account for
It prices the project, not the outcome. The numbers it cannot see are mostly about tax, time and the market moving underneath you.
- Tax on the profit; flips are taxed, and how much depends on whether you buy personally or through a company
- Holding costs while you own it: council tax, utilities, insurance and upkeep during the works
- Time, which the margin ignores; a 20% margin over two years can be a worse outcome than 12% in four months
- The market moving between purchase and sale, in either direction
- Whether the GDV itself is right, which no spreadsheet can verify for you
How often flips stack
Appraise enough properties and the honest pattern is that most do not work at the asking price. Of 3,023 appraisals PropDetect has run, 67.5% did not stack. That is not a reason to avoid flipping; it is the base rate that makes disciplined filtering the actual job, and a calculator that says no most of the time is doing its work.
On the cost side, the median modelled refurbishment across 2,545 PropDetect-analysed properties is £11,795 including VAT, as of 5 September 2026. A full structural flip will sit well above that median, but if your refurb line is a guess, the regional cost data linked under the calculator is a better anchor than optimism.
Frequently asked questions
What is a good profit margin on a flip?
Common practice among UK flippers and development lenders treats 15 to 20% of GDV as the working range, with anything much below 15% leaving little room for error. It is a convention rather than a rule, but it exists because down-valuations, overruns and slow sales are routine, not exceptional.
What is margin on GDV?
Profit divided by the end sale value, expressed as a percentage. A £37,500 profit on a £240,000 sale is a 15.6% margin on GDV. It is a stricter test than return on cost because the denominator is bigger, and it is the framing most development lenders use.
What buying and selling costs should I include?
Buying: stamp duty including the additional property surcharge, legals, survey and broker fees. Selling: estate agent commission and legal fees. Finance sits in its own box: bridge interest, arrangement and exit fees over the realistic project length, not the optimistic one.
Why add a contingency to the refurb?
Because the refurb estimate is the least certain number in the appraisal. Opened-up walls, hidden damp and price rises mid-project all land on the same budget line. A 15% contingency prices that uncertainty in from the start instead of discovering it at month four.
Want this run automatically on any Rightmove listing?
PropDetect runs these numbers, and the rest of the deal, on every listing that matches your criteria: refurb costs from the photos, comparable sold valuations, rent, GDV and a strong, solid or avoid verdict across six strategies. You just read the result.
More free calculators
- Stamp duty calculator (SDLT, LBTT and ADS)
Banded SDLT and LBTT with the additional-property surcharge and Scottish ADS done properly, band by band.
- Bridging loan calculator
Total cost of a bridge from monthly rate, term and fees, with the monthly-not-annual quoting explained.
- HMO yield calculator
Gross and net yield on total money in for a room-let HMO, with bills, management and voids included.
- Rental yield calculator
Work out gross and net rental yield from purchase price, rent and running costs.
- GDV calculator
Estimate gross development value from comparable sales, with a price-per-sqft cross-check.
- BRRR calculator
Model buy, refurbish, rent, refinance: cash left in, cashflow and return on the money still in the deal.
- Property ROI calculator
Return on investment for a purchase and refurb, on a sale or a rental exit.
- Refurb cost calculator
Kitchen, bathroom, decorating, flooring and electrics priced by condition level and region, with the 15% contingency built in.