Useful next calculations
When to use this calculator
- Before choosing between saving, investing or changing a contribution.
- When you want to compare cautious, base and optimistic return assumptions.
- When you need a projection before making a longer-term decision.
- When you want to see whether starting earlier or contributing more changes the outcome more.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Gross taxable interest for the tax year (£) | £1,500 |
| Savings tax band | Basic rate |
For those figures the calculator returns:
- Personal Savings Allowance: £1,000.00
- Taxable interest: £500.00
- Estimated tax: £100.00
- Interest after tax: £1,400.00
How to read your results
Taxable Interest
Review this figure alongside your gross income so you can understand deductions before the tax year closes. It is a planning estimate, not a filed return.
Estimated Tax
Review this figure alongside your gross income so you can understand deductions before the tax year closes. It is a planning estimate, not a filed return.
Interest After Tax
Review this figure alongside your gross income so you can understand deductions before the tax year closes. It is a planning estimate, not a filed return.
Method & assumptions
This 2026/27 estimate applies the Personal Savings Allowance to gross taxable interest using the tax band you select. It then applies the corresponding savings-tax rate to interest remaining above that allowance.
It deliberately excludes ISA interest and does not guess your tax band from salary. The personal allowance, starting rate for savings, joint accounts, trusts, foreign interest, Scottish ordering and a complete Self Assessment position can alter the final result.
Use HMRC guidance and your own tax records before filing or changing an account. Savings tax rates change from 2027/28, so rerun the calculation for later years.
Common mistakes
- Assuming a constant return without checking a more conservative growth rate.
- Forgetting ongoing contributions, fees or tax wrappers where relevant.
- Focusing only on the final balance instead of the path required to reach it.
- Ignoring the drag of charges over a long period.
What to do next
- Test a cautious, expected and optimistic growth rate.
- Compare this result with related savings or retirement tools before committing more money.
- Consider charges and any tax wrapper that applies.
- If the projected balance falls short, increase the contribution until the result meets your goal.