Continue your plan
Useful next calculations
Rates & sources
A user-entered cash-flow illustration that turns predictable annual costs into a monthly sinking-fund target and compares quiet, typical and strong income months. It does not predict income or assess tax liabilities.
Source: MoneyHelper — Budget planner — check the linked guidance and any live quote before acting.
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
A realistic UK planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Conservative monthly income (£)
£35,000
Essential monthly costs (£)
6
Predictable annual irregular costs (£)
£500
After entering these figures, review monthly sinking-fund target and low-month surplus after essentials together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Monthly Sinking-Fund Target
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Low-Month Surplus After Essentials
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This planner helps households with variable earnings build a plan from a conservative month rather than the best month. It converts predictable annual costs into a monthly sinking-fund target and shows the surplus or deficit at low, typical and stronger income levels.
The accessible buffer is compared with a low-month deficit only; it is not an insurance policy or a complete emergency-fund recommendation.
Income, work patterns, tax, benefits and debt commitments can all change quickly. Use actual records, update the plan often and seek free independent advice before missing payments or taking new borrowing.
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes, or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures and total costs.
- !Not accounting for the impact of a rate revert after an introductory fixed period ends, which can sharply increase payments.
What to do next
- Run a second scenario with a higher rate or shorter term so you can see the downside clearly.
- Compare the result with an affordability or overpayment calculator before applying.
- Use the related guides below to understand trade-offs before you request live quotes.
- Note down the monthly payment and total interest for your two or three strongest scenarios so you have a clear comparison ready when you speak to a broker.
- Check whether making a modest overpayment each month would reduce total interest significantly — run the overpayment calculator next to find out.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.