Shared Ownership Calculator: True Cost & Staircasing
See what a shared ownership home costs year by year — rent, service charge and mortgage — how staircasing changes it, and how it compares with buying outright or renting.
Every assumption is shown and can be changed. Illustration, not advice.
Your figures
Illustration, not advice- Total spend over 25 years
- £391,902
- First-year monthly cost
- £1,012
- Share owned at the end
- 25%
- Equity at the end
- £123,045
- Mortgage left at the end
- £0
| Year | Rent | Service charge | Interest | Capital repaid | Staircasing | Home value | Equity |
|---|---|---|---|---|---|---|---|
| 1 | £6,188 | £1,200 | £3,174 | £1,578 | £0 | £306,000 | £6,828 |
| 2 | £6,373 | £1,236 | £3,101 | £1,651 | £0 | £312,120 | £10,009 |
| 3 | £6,564 | £1,273 | £3,026 | £1,727 | £0 | £318,362 | £13,297 |
| 4 | £6,761 | £1,311 | £2,946 | £1,806 | £0 | £324,730 | £16,695 |
| 5 | £6,964 | £1,351 | £2,863 | £1,889 | £0 | £331,224 | £20,207 |
| 6 | £7,173 | £1,391 | £2,777 | £1,976 | £0 | £337,849 | £23,839 |
| 7 | £7,388 | £1,433 | £2,686 | £2,067 | £0 | £344,606 | £27,595 |
| 8 | £7,610 | £1,476 | £2,591 | £2,162 | £0 | £351,498 | £31,480 |
| 9 | £7,838 | £1,520 | £2,492 | £2,261 | £0 | £358,528 | £35,498 |
| 10 | £8,073 | £1,566 | £2,388 | £2,365 | £0 | £365,698 | £39,655 |
| 11 | £8,315 | £1,613 | £2,279 | £2,473 | £0 | £373,012 | £43,957 |
| 12 | £8,565 | £1,661 | £2,165 | £2,587 | £0 | £380,473 | £48,409 |
| 13 | £8,822 | £1,711 | £2,047 | £2,706 | £0 | £388,082 | £53,017 |
| 14 | £9,087 | £1,762 | £1,922 | £2,830 | £0 | £395,844 | £57,788 |
| 15 | £9,359 | £1,815 | £1,792 | £2,960 | £0 | £403,761 | £62,727 |
| 16 | £9,640 | £1,870 | £1,656 | £3,096 | £0 | £411,836 | £67,842 |
| 17 | £9,929 | £1,926 | £1,514 | £3,238 | £0 | £420,072 | £73,140 |
| 18 | £10,227 | £1,983 | £1,365 | £3,387 | £0 | £428,474 | £78,627 |
| 19 | £10,534 | £2,043 | £1,210 | £3,543 | £0 | £437,043 | £84,313 |
| 20 | £10,850 | £2,104 | £1,047 | £3,705 | £0 | £445,784 | £90,203 |
| 21 | £11,175 | £2,167 | £877 | £3,876 | £0 | £454,700 | £96,308 |
| 22 | £11,511 | £2,232 | £699 | £4,054 | £0 | £463,794 | £102,635 |
| 23 | £11,856 | £2,299 | £512 | £4,240 | £0 | £473,070 | £109,194 |
| 24 | £12,212 | £2,368 | £318 | £4,435 | £0 | £482,531 | £115,994 |
| 25 | £12,578 | £2,439 | £114 | £4,639 | £0 | £492,182 | £123,045 |
Your lease sets the actual rent review terms; these figures use the new model rules you selected. House prices are assumed to grow 2% a year — an assumption, and prices can fall.
No staircasing yet. Add a step to see how buying more shares changes your rent, mortgage and equity.
Planned ownership: 25%. Each step is priced at the home's assumed value in that year, plus a £350 valuation and £500 legal fee (not charged on 1% steps in years 1–15).
| Year | Staircasing cost | Paid from savings | Share owned | Mortgage balance | Rent |
|---|---|---|---|---|---|
| 1 | £0 | £0 | 25% | £69,672 | £6,188 |
| 2 | £0 | £0 | 25% | £68,021 | £6,373 |
| 3 | £0 | £0 | 25% | £66,294 | £6,564 |
| 4 | £0 | £0 | 25% | £64,488 | £6,761 |
| 5 | £0 | £0 | 25% | £62,599 | £6,964 |
| 6 | £0 | £0 | 25% | £60,623 | £7,173 |
| 7 | £0 | £0 | 25% | £58,556 | £7,388 |
| 8 | £0 | £0 | 25% | £56,395 | £7,610 |
| 9 | £0 | £0 | 25% | £54,134 | £7,838 |
| 10 | £0 | £0 | 25% | £51,769 | £8,073 |
| 11 | £0 | £0 | 25% | £49,296 | £8,315 |
| 12 | £0 | £0 | 25% | £46,709 | £8,565 |
| 13 | £0 | £0 | 25% | £44,003 | £8,822 |
| 14 | £0 | £0 | 25% | £41,173 | £9,087 |
| 15 | £0 | £0 | 25% | £38,213 | £9,359 |
| 16 | £0 | £0 | 25% | £35,117 | £9,640 |
| 17 | £0 | £0 | 25% | £31,878 | £9,929 |
| 18 | £0 | £0 | 25% | £28,491 | £10,227 |
| 19 | £0 | £0 | 25% | £24,948 | £10,534 |
| 20 | £0 | £0 | 25% | £21,243 | £10,850 |
| 21 | £0 | £0 | 25% | £17,367 | £11,175 |
| 22 | £0 | £0 | 25% | £13,313 | £11,511 |
| 23 | £0 | £0 | 25% | £9,073 | £11,856 |
| 24 | £0 | £0 | 25% | £4,639 | £12,212 |
| 25 | £0 | £0 | 25% | £0 | £12,578 |
| Option | First-year monthly | Cash paid out over 25 years | Equity at the end |
|---|---|---|---|
| Shared ownership | £1,012 | £391,902 | £123,045 |
| Buy the whole home | £1,747 | £541,497 | £492,182 |
| Rent the same home | £1,125 | £492,200 | £0 |
Buying the whole home with the same deposit needs a 98.75% loan-to-value mortgage. Most lenders cap here at 95%, so this option may not be available with this deposit.
Cash paid out and equity are shown side by side rather than combined into one answer: which matters more depends on how long you stay and what you plan to do next. If you would like a view on your own plans, an adviser can look at your situation.
These figures show what the home could cost. Whether a lender will lend on your share depends on your income, commitments and the lender's own rules for rent and service charge. Our free check takes these numbers straight into the lender search.
See which lenders would lend on thisFree. No credit search.
How shared ownership costs work
You pay three things each month: a mortgage on the share you buy, rent to the housing association on the share you don't own, and a service charge. Your deposit only needs to cover the share you're buying, which is why shared ownership can be a way in with a smaller deposit.
A worked example. A £300,000 home, buying 25% with a £3,750 deposit, a 4.5% mortgage over 25 years, rent at 2.75% of the unsold share and a £100 a month service charge: the first year costs about £1,012 a month and total spend over 25 years is about £391,902, leaving £123,045 of equity if prices rise 2% a year.
Staircasing changes the picture. Buying another 25% in year 5 and the final 50% in year 10, both added to the mortgage, means owning 100% with total spend of about £604,338 and £492,182 of equity at the end, on the same growth assumption. Prices can fall as well as rise, and a lower value makes each step cheaper.
New model and older leases
| Rule | New model (2021+) | Older lease |
|---|---|---|
| Minimum first share | 10% | 25% |
| Minimum staircasing step | 5% | 10% |
| 1% yearly steps | Years 1–15, no valuation or legal fee | Not available |
| Yearly rent increase | CPI + 1% | RPI + 0.5% |
What staircasing costs
Each step is priced at the home's value at the time, so the calculator grows the price by your house price assumption. On top of the share price there is usually a valuation and legal work — set at £350 and £500 here, and not charged on new-model 1% steps in the first 15 years. You can pay from savings or add the cost to your mortgage; borrowing spreads it over the rest of your term.
Frequently asked questions
How is shared ownership rent worked out?
Rent is charged on the share you do not own. It is commonly 2.75% a year of that share's value when you buy, and some older schemes charge up to 3%. It then rises once a year under your lease: usually CPI + 1% on new-model leases and RPI + 0.5% on older ones. Your lease sets the actual terms.
What is staircasing?
Staircasing is buying more shares in your home after you move in. Each extra share is priced at the home's market value at the time, not what you originally paid, so rising prices make it dearer. Your rent falls in proportion to the share you buy, and stops once you own 100%. A service charge usually continues, especially for flats.
What changed with the new shared ownership model?
Homes under the 2021 model can start from a 10% share (previously 25%), let you buy extra shares in steps from 5% (previously 10%), and allow 1% steps each year for the first 15 years with no valuation or legal fee. Rent reviews are capped at CPI + 1%. Check which model your lease uses: the calculator lets you switch.
Is shared ownership cheaper than buying outright or renting?
It depends on how long you stay, how house prices move and whether and when you staircase. The Compare tab shows cash paid out and equity at the end side by side rather than picking one for you. If you want a view on your own plans, an adviser can look at your situation.
Can I get a mortgage for a shared ownership home?
Yes. 32 lenders on our panel lend on shared ownership. They assess the mortgage on your share together with the rent and service charge. The Your check tab sends these figures into our free lender check.
Found a home? Check which lenders would lend on your share
Our free check counts the rent and service charge the way lenders typically do, across 32 shared ownership lenders.
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Compare renting against buying over time, including opportunity cost.
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SDLT for England and Northern Ireland, including first-time-buyer relief.
How this calculator works, and when it was last checked
- Method
- A year-by-year projection. The mortgage on your share is repaid monthly; rent on the share you don't own rises by CPI + 1% (new model) or RPI + 0.5% (older lease) and falls in proportion when you staircase; each staircasing step is priced at the home's assumed value that year. Every assumption is shown and can be changed — it is an illustration, not a figure from your housing association.
- Calculation last verified
- — Projection checked against independently hand-worked figures for both lease models, staircasing funded by borrowing and by savings, the 1% step fee waiver, and the buy-outright and renting comparisons. This tool does not rely on a rate table we maintain, so it does not go out of date when rates move.
- Who checked it
- Reviewed by Phillip Wakeling-Smith, CeMAP-qualified mortgage adviser.
Results are an estimate for general information, not a quote, an offer of credit, or advice. Your own figures depend on a lender's full assessment of your circumstances.
