Shared Ownership Mortgage Calculator

Welcome to our Shared Ownership mortgage calculator hub. At the top of this page, you will find a free calculator tool that can tell you how much your Shared Ownership mortgage will cost, with rent payments factored in, and also help you with your staircasing needs.

Give our calculator a try and don’t hesitate to reach out once you’ve crunched the numbers so one of our Shared Ownership specialists can go through your options with you.

What our Shared Ownership calculator can tell you

With our Shared Ownership calculator, you can work out two things:

• How much the repayments will be on a mortgage taken out through the scheme

• How much your payments will change if you buy extra shares (staircasing)

In addition to this, you can compare the cost of your mortgage across different interest rates, get an idea of how quickly you can achieve full ownership through staircasing, compare repayment deals with interest-only and explore the implications of different term lengths.

How this calculator works

To use our Shared Ownership mortgage calculator, first select whether you are looking for repayment or staircasing figures by choosing the relevant check box on the tool.

Working out your repayments

To calculate the repayments on a mortgage taken out through the Shared Ownership scheme, our tool will prompt you to enter the following information:

• The amount you are borrowing

• Mortgage term length

• Repayment type (capital repayment or interest-only)

• Interest rate

• Monthly rent payment

Once you have entered this information and hit ‘calculate’ our tool will offer a breakdown of how much your monthly payments will be, what the overall cost of your mortgage would look like, and how much you will have paid in interest and rent payments across the whole term.

Calculating your staircasing

If you choose the staircasing option, you can work out how much your mortgage payments will change if you buy additional shares of your property, all the way up to 100% of it.

To work this out, the calculator will prompt you to enter the following:

• Current property value

• Current ownership

• Target Ownership

• Monthly rent

• Service charge

• Mortgage rate

• Term length

The output will tell you what it will cost to buy an extra share of your home, what percentage of ownership this will take you to, and how your payments will change as a result.

Why use our Shared Ownership mortgage calculator?

Most mortgage calculators will simply tell you how much you can borrow and what the repayments will be on a regular mortgage, but this one is specially tailored to the needs of a homebuyer or homeowner who is using the Shared Ownership scheme.

It is a usually starting point on your journey, whether you are planning to apply for a new mortgage through the scheme or increase your share in a Shared Ownership property.

Here is what our calculator is useful for:

• Getting clarity on your mortgage costs for budgeting and planning purposes

• Planning a staircasing application with accurate numbers in mind

• Comparing repayment results across different interest rates

• Comparing repayment results with interest-only figures

• Exploring how term length impacts the cost of your mortgage

One thing to keep in mind is that all online mortgage calculators can only provide rough estimates of what your mortgage costs will look like. They aren’t bespoke to you, which is why it’s a good idea to seek professional advice after running your numbers.

Below you can access a free, no-obligation chat with a Shared Ownership mortgage specialist who can provide personalised calculations and tailored advice on your mortgage options based on these numbers, as well as your needs and circumstances.

Example calculations

Here you will find example calculations for a Shared Ownership mortgage and staircasing scenarios produced by our calculator tool.

1. Repayment calculation examples

This mode helps users budget for their monthly outgoings by combining mortgage repayments with the rent paid on the share they don't own.

Scenario A: The first-time buyer

• Borrowing Amount: £150,000

• Term: 25 Years

• Interest Rate: 5%

• Monthly Rent: £350

2. Staircasing calculation examples

This mode calculates how much it costs to increase your ownership percentage and how that shift affects your monthly payments.

Scenario B: Increasing Ownership (Staircasing)

• Current Property Value: £300,000

• Current Ownership: 25%

• Target Ownership: 50% (Buying an extra 25% share)

• Current Monthly Rent: £500

• Mortgage Rate: 4.5%

*Rent typically decreases because you own more of the property. **Assumes the £75,000 is added to the mortgage.

3. Comparison: Repayment vs. Interest-Only

The tool allows users to compare different repayment structures to see how they impact monthly cash flow versus long-term cost.

• Loan Amount: £200,000

• Rate: 4%

• Term: 30 Years

How affordability is calculated for a Shared Ownership mortgage

Unlike standard mortgages that focus primarily on a salary multiple, Shared Ownership affordability assessments must account for three distinct monthly costs: mortgage repayments, subsidised rent, and service charges.

The assessment methodology follows updated Homes England guidance, which prioritises long-term sustainability over simply "maximising" the share a person can buy.

The affordability calculation process

1. Income and debt analysis

Advisors begin by calculating your Net Mortgageable Income.

• Gross Income: This includes basic salary plus 50% of any overtime, bonuses, or commission.

• Deductions: Tax, National Insurance, and student loans are deducted.

• Debt Commitments: Monthly payments for personal loans and hire purchase are deducted. For credit cards, 3% of the total outstanding balance is typically used as a monthly cost (equivalent to 36% per year).

2. The 45% household expenditure cap

A central pillar of affordability is the ratio of housing costs to net income.

• The Rule: Total housing costs (mortgage + rent + service charge) should generally not exceed 45% of your net household income.

• The Lower Limit: To ensure you are contributing enough, total housing costs should ideally be at least 25% of your net wage.

• The Goal: This leaves roughly 55% of your income for other essential living costs like food, fuel, and childcare.

3. Stress testing

To ensure you can afford the home in the future, advisors "stress test" your figures against potential changes:

• Rent Stress Test: Rent is often stress-tested at a higher rate (e.g., 3.5%–3.6%) to account for annual increases, which are typically linked to indices like CPI + 1% or RPI + 0.5%.

• Mortgage Stress Test: Lenders apply their own interest rate stress tests to ensure you could still meet payments if rates rise.

4. Surplus income policy

Many providers require a "buffer" to protect you against unforeseen expenses.

• The 10% Buffer: It is common practice to require that you have at least 10% of your net income remaining after all housing costs and essential expenditures (as identified in a budget planner) have been paid.

Key affordability indicators

Why choose Money Helpdesk for your mortgage needs?

Aside from providing you with bespoke calculations and expert advice about how to act on them, our mortgage brokers are whole-of-market and specialise in Shared Ownership.

Here are just some of the reasons why Shared Ownership mortgage applicants choose us:

• Exclusive rates and deals are available

• Our mortgage brokers have access to the entire market

• We are five-star rated on leading review websites

• You can secure an agreement in principle in minutes

Ready to take advantage of a free, no-obligation chat with a mortgage broker who specialises in the Shared Ownership scheme? Get started here.

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