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How it works
A normal monthly budget is useful — but some household costs don’t happen every month.
Budget Lens looks a little further ahead.
01
Start with your usual month
Enter the monthly household spending figure you normally work with.
02
Look beyond the usual month
Think about costs coming up over the next 12 months — things like annual insurance, road tax, school expenses or other irregular costs.
03
Bring it into one monthly view
Budget Lens works out what those costs mean across the next 12 months, while checking what your existing monthly figure already includes.
The result is a broader monthly planning figure — without counting the same cost twice.
For the thinking behind this fuller view, read why a monthly budget can still miss part of the year.
See what changes
Adding an irregular cost does not always mean adding the whole amount on top of your current budget.
Sometimes the cost is missing from your monthly figure. Sometimes part or all of it is already there. And sometimes another reliable source will cover part of the cost.
Budget Lens accounts for those differences.
If a cost was missing
Its relevant next-12-month amount increases your monthly planning figure.
If it was already included
Budget Lens replaces what was already represented with what the cost is expected to be over the next 12 months.
If the cost becomes lower
Your monthly planning figure can fall too.
That is why the calculation is not simply:
monthly budget + every annual bill ÷ 12
The aim is to see the next 12 months more clearly — not to count things twice.
FAQ
No. Some months will naturally be higher and others lower.
The figure turns the relevant costs of the next 12 months into a monthly equivalent so you can see the year through a more useful monthly lens.
It does not change when the bills themselves are due.
Not necessarily.
Budget Lens is a planning tool, not a savings prescription. Your result can help you think about how much your household needs to support over time, but how you organise cash, sinking funds or savings is a separate decision.
Use a figure that reasonably represents what your household normally spends from ordinary spendable household money.
It does not have to be a perfect reconstruction of every transaction.
The more representative your starting figure is, the more useful the comparison becomes.
Include household costs you can reasonably foresee within the next 12 months, even if they do not happen every month.
They might be annual, seasonal, occasional or one-off costs.
Budget Lens is not intended to predict completely unexpected emergencies.
Tell Budget Lens that it is already represented.
The calculator can then adjust that existing amount rather than simply adding the cost again.
This is an important part of the count-once approach.
A reliable amount specifically linked to that expense can be taken into account.
Funding that is uncertain, hoped for, or not actually available for that expense should not be used to reduce the cost.
Twelve months is long enough to catch many expenses that disappear from an ordinary monthly view — annual bills, school costs, seasonal spending and other irregular expenses — while still keeping the planning period close enough to be useful.
The window moves with you. It is the next 12 months, not necessarily January to December.
Unknown is different from zero.
If a relevant cost is still genuinely unknown, Budget Lens should not quietly treat it as though the cost does not exist.
Use the best reasonably reliable information you have before relying on the final figure.
Methodology & assumptions
Budget Lens is built around one simple idea:
Every relevant household cost should appear once in the next-12-month picture — not zero times, and not twice.
The calculator starts with a representative current monthly spending figure and then looks for costs that may be hidden, changing or already partly represented inside it.
For each relevant cost, Budget Lens works on a consistent next-12-month basis.
A few principles sit underneath the calculation:
- Costs are included when they are reasonably foreseeable within the next 12 months.
- A one-off cost can still belong in the calculation if it falls within that period.
- Completely unexpected shocks are outside the scope of the tool.
- Costs already represented in the starting monthly figure are adjusted rather than added again.
- Reliable funding or resources specifically available for a cost can reduce the amount that has to come from ordinary household spending.
- The same funding or reduction cannot be used twice.
- Savings, investments and transfers into reserves are not treated as household expenditure simply because money moves out of the spending account.
- Where something is financed, Budget Lens counts the relevant obligations falling within the 12-month period rather than counting both the full purchase price and the repayments.
- Amounts that are genuinely recoverable, such as a recoverable deposit, are not automatically treated as a final household cost.
The result is therefore a planning view, not an accounting statement and not a forecast of the exact cash leaving your account each month.
Calculation details
You do not need this section to use Budget Lens. It is here for anyone who wants to see what is happening underneath.
At a glance
- Your current monthly spendingYour usual monthly budget.
- Work out each cost’s next 12 monthsFind the relevant amount for each cost.
- Account for reliable funding and what is already includedSubtract relevant reliable funding and avoid counting an amount already represented in the starting monthly figure.
- Spread the adjustment over 12 monthsConvert the net 12-month change into a monthly equivalent.
- Your monthly planning figureYour updated monthly planning amount.
In plain English
Budget Lens starts with your usual month, finds what each relevant cost will need from ordinary household spending, adjusts for anything already included, then spreads the change over 12 months.
The calculation
For those who want the exact details.
B = your representative current monthly household spending.
1. Ordinary household cost
For each cost, first find the relevant next-12-month amount that needs to come from ordinary household resources.
2. 12-month adjustment
Compare that cost with anything for the same cost already represented in your current monthly figure.
3. Monthly planning figure
Spread the combined adjustments over 12 months and apply them to your current monthly spending.
Another way to read the same calculation is:
If a cost was completely missing, its monthly equivalent is added. If it was already fully and accurately represented, there may be little or no change.
If the amount expected over the next 12 months is lower than what your current budget already carries, the adjustment can be negative.
This replacement approach keeps each underlying cost in the picture exactly once.
Calculations use the underlying values before the displayed figures are rounded, so rounding shown on screen does not change the calculation itself.