Welcome to the Half Buy Half Rent Calculator! This tool is designed to make shared ownership housing costs easy to understand. If you’re considering a half buy, half rent scheme (sometimes called shared ownership), it helps you figure out how much you’ll need for your initial purchase, mortgage payments, monthly rent, and any additional fees. Instead of manually crunching numbers, the calculator handles it all for you, so you can focus on whether this housing option fits your lifestyle and budget.
You can begin using the calculator right now, or continue reading to learn about the formulas, parameters, and examples that explain exactly how it works.
Understanding the Formula
The Half Buy Half Rent Calculator is built around a few key equations that determine both upfront and ongoing costs.
Initial Purchase Costs
-
Value of Share Purchased:
Value of Share Purchased = Full Property Value × (Ownership Share Percentage / 100) -
Mortgage Amount Needed:
Mortgage Amount Needed = Value of Share Purchased − Deposit Amount -
Value of Share Rented:
Value of Share Rented = Full Property Value − Value of Share Purchased
Monthly Costs
-
Monthly Mortgage Payment (Amortization Formula):
M = P × [r(1+r)^n] / [(1+r)^n − 1]
- M = Monthly Mortgage Payment
- P = Mortgage Amount Needed
- r = Monthly Interest Rate (Annual Rate / 12 / 100)
- n = Total Number of Payments (Years × 12)
-
Monthly Rent Payment:
Monthly Rent = (Value of Share Rented × (Annual Rent Percentage / 100)) / 12 -
Total Monthly Housing Cost:
Total Monthly Cost = Monthly Mortgage Payment + Monthly Rent + Other Monthly Fees
Put simply: the formulas help you understand how much you’ll pay upfront, what your loan repayment will look like, how much rent you’ll owe on the share you don’t own, and what the total monthly cost comes to.
Parameters Explained
Full Property Value
The total market price of the property before splitting ownership.
Ownership Share Percentage
The portion you choose to buy—often 50% in “half buy, half rent,” but it could be higher or lower.
Deposit Amount
The upfront cash you put toward your purchased share. A larger deposit reduces the mortgage needed.
Mortgage Amount Needed
The portion you borrow from the lender to cover your ownership share.
Annual Interest Rate
The percentage charged on your mortgage loan, usually quoted yearly.
Mortgage Term (Years)
The length of time you’ll take to repay the mortgage—commonly 20, 25, or 30 years.
Annual Rent Percentage
The percentage charged by the housing association or landlord on the rented portion of the property.
Other Monthly Fees
Includes service charges, ground rent, or building management costs.
How to Use the Half Buy Half Rent Calculator — Step-by-Step Example
Let’s go through an example to see how the calculator works.
- Full Property Value = £200,000
- Ownership Share Percentage = 50%
- Value of Share Purchased = 200,000 × 0.5 = £100,000
- Deposit Amount = £10,000
- Mortgage Amount Needed = 100,000 − 10,000 = £90,000
- Value of Share Rented = 200,000 − 100,000 = £100,000
- Mortgage: Assume 4% annual interest rate, 25-year term (n = 300 months).
- Monthly Mortgage Payment ≈ £474
- Rent: Annual Rent Percentage = 3%
- Monthly Rent = (100,000 × 0.03) ÷ 12 = £250
- Other Fees = £50
Total Monthly Housing Cost = 474 + 250 + 50 = £774
Result: In this example, you’d pay £774 per month in total housing costs.
Additional Information
Here’s a quick comparison of typical scenarios:
| Share Purchased | Deposit | Monthly Mortgage | Monthly Rent | Total Cost (with £50 fees) |
|---|---|---|---|---|
| 50% (£100,000) | £10,000 | £474 | £250 | £774 |
| 60% (£120,000) | £12,000 | £569 | £200 | £819 |
| 40% (£80,000) | £8,000 | £379 | £300 | £729 |
This table shows how your monthly payments change depending on the share you choose to buy.
FAQs
It means you purchase part of the property (often 50%) with a mortgage and deposit, while paying rent on the remaining share.
No. While 50% is common, you can often buy more or less, depending on the scheme and your budget.
Yes, many shared ownership programs allow “staircasing,” where you gradually buy more of the property over time.