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Shared ownership calculator
See the monthly cost of buying a share, made up of the mortgage, the rent on the part you don’t own and the service charge. Change the share to see what staircasing does.
Monthly cost
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Enter the value and mortgage rate.
- Last checked 25 October 2026
- Expert review pending
- How we calculate
How this is calculated
- Mortgage: your share of the value, less the deposit, repaid over the term at the rate you enter, as a standard repayment mortgage.
- Rent: the value of the share you don’t own × the rent rate ÷ 12.
- Service charge: added as entered.
The figures are for the first year. Rent normally rises each year by the formula in your lease, and the mortgage changes when a fixed rate ends.
Worked example
25% of a £320,000 flat
Your share is £80,000. With a 10% deposit (£8,000) you borrow £72,000. Over 30 years at 4.5% that is about £364.81 a month. Rent on the other £240,000 at 2.75% is £550 a month. With a £120 service charge the total is about £1,034.81 a month. Staircasing to 50% would cut the rent to £366.67.
Questions people ask
How much rent do you pay on shared ownership?
Rent is charged on the share you don’t own. Leases usually set the starting rent at up to 2.75% or 3% of the value of that share each year, then increase it once a year by a formula in the lease, often linked to inflation. Your lease and the housing association’s key information document give the exact figures.
What is staircasing?
Buying more shares in the home. Each share is priced at the market value when you buy it, not the original price, and the rent drops in proportion. Under the newer model lease you can buy 1% a year for the first 15 years with reduced fees, as well as larger shares of 5% or more.
Do I pay a service charge on top?
Usually yes, and it covers the whole building or estate, not just your share. On flats it can be a large part of the monthly cost, so ask for the last few years’ figures before you commit.
Is shared ownership available in Scotland, Wales and Northern Ireland?
Each nation runs its own schemes. Scotland has shared equity and shared ownership through housing associations, Wales has Homebuy and shared ownership, and Northern Ireland has Co-Ownership. The maths in this calculator works the same way, but rents and rules differ.