Budgeting

Cash-Flow Calendar & Payday Buffer Calculator

A budget can be positive for the month and still fail on day 22 because bills leave before income arrives. This tool focuses on timing, not just totals.

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Starting position

Set the cash available and main payday.

£
£

Bills and collection dates

Add predictable outgoings.

Bills

Your estimate

Use the result as a planning guide and change inputs to test the assumptions that matter most.

How this calculator works

The calculator simulates a 31-day planning month. It adds income on the payday entered and deducts each bill on its day, tracking the lowest balance and ending balance.

How to use it

  1. Enter the balance available at the start of the planning month.
  2. Add monthly income and the day it lands.
  3. Add fixed or predictable bills with their collection day.
  4. Review the lowest-balance day and buffer estimate.
  5. Consider changing collection dates or holding a buffer if timing is the problem.

Assumptions and limitations

This simplified calendar uses one monthly income event and 31 days. Weekends, bank holidays, variable card spending and multiple pay cycles can change real cash flow.