Shared Ownership Calculator

Calculate the true monthly cost of shared ownership including mortgage payments, rent on the housing association's share, and the impact of staircasing over time.

Shared ownership lets you buy a share of a property (typically 25% to 75%) and pay rent on the rest to a housing association. It is one of the main routes onto the housing ladder for first-time buyers who cannot afford a full purchase, but the true monthly cost is often higher than people expect.

On top of your mortgage repayment, you pay rent to the housing association at a capped percentage of the unsold share. Service charges, ground rent (on older leases), and buildings insurance add further costs. Over time, you can “staircase” — buy additional shares — to reduce your rent and eventually own the property outright.

The Ministry of Housing reported that over 22,000 shared ownership homes were completed in England in 2023/24 (GOV.UK Affordable Housing Supply). Understanding the full picture before committing is essential.

How this calculator works

  1. Enter the full property value, the share you plan to buy, and your deposit.
  2. Set the mortgage rate, rent percentage on the unsold share, and any service charges.
  3. The tool shows your total monthly cost, the impact of staircasing at different intervals, and a comparison against renting or full ownership.

Written by the CalcStack team · Last updated April 2026

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Typically RPI + 0.5% (default 3.5%)

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Show staircasing analysis (buying more shares over time)

Frequently asked questions

What is shared ownership?
Shared ownership lets you buy a share of a home (usually 25-75%) and pay rent on the remaining share to a housing association. You need a smaller deposit and mortgage than buying outright, making it a popular route onto the property ladder for first-time buyers.
How much deposit do I need for shared ownership?
You typically need a 5-10% deposit on your share, not the full property value. So for a £300,000 property at 25% share (£75,000), a 5% deposit would be just £3,750. This is much more achievable than the £15,000-30,000 needed for a full purchase.
What is staircasing in shared ownership?
Staircasing means buying additional shares in your home over time. You can typically buy extra shares in increments of 10% or more until you own 100%. The cost is based on the current market value at the time of staircasing, so if the property has increased in value, each additional share costs more.
Can I sell a shared ownership home?
Yes, but the housing association usually has the right to find a buyer first (within a set period, typically 8 weeks). If they cannot find a buyer, you can sell on the open market. If you own 100% through staircasing, you can sell freely.
How is the rent calculated on shared ownership?
The rent is set by the housing association, typically at 2.75% of the housing association's share value per year. Annual increases are usually capped at RPI + 0.5%, though some newer schemes use CPI + 1%. The rent reduces as you staircase to own more of the property.
What are the downsides of shared ownership?
Key downsides include: you pay both mortgage and rent; rent increases can outpace wage growth; staircasing costs more if property values rise; there may be restrictions on alterations; selling can take longer; and you may face service charges. The total monthly cost can sometimes exceed renting.
Is shared ownership available to everyone?
Shared ownership is primarily aimed at first-time buyers, but existing shared owners and those who used to own a home may also qualify. Your household income must be £80,000 or less (£90,000 in London). You must also be unable to afford to buy a suitable home outright.
What stamp duty do I pay on shared ownership?
You can choose between two options: pay stamp duty on your initial share only (and again when you staircase past 80%), or pay stamp duty on the full market value upfront. For most buyers at 25%, paying on the share is cheaper. This calculator uses the share-only method.
Can I remortgage a shared ownership property?
Yes, you can remortgage when your fixed rate ends, just like any other mortgage. However, fewer lenders offer shared ownership mortgages, so your options may be more limited. You will need the housing association's permission to switch lenders.
What happens if property prices fall?
If property prices fall, the value of your share falls too. Staircasing becomes cheaper (you buy additional shares at current value), but if you need to sell, you might get less than you paid. You are responsible for your mortgage regardless of the property's value.

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