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Founder Finances

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13-Week Cash-Flow Forecaster

Find the week your balance dips lowest, before it happens.

A rolling 13-week view is the standard small-business cash tool. Enter your opening balance and typical weekly movements, add one known lumpy payment, and see where the floor is.

Last reviewed:

Your figures

Results update as you type. The starting figures are examples; replace them with your own. Financial inputs stay in your browser unless you choose to save them on this device.

Money actually available today, across all business accounts.

Be conservative. Only count money you genuinely expect to land.

Include your own pay, subcontractors, software and premises.

VAT, corporation tax, an annual renewal — enter 0 if none.

The level below which you would start making bad decisions.

Your result

£8,800

Lowest projected balance over 13 weeks

Occurs in week 7

Week 1
£12,400
Week 2
£12,800
Week 3
£13,200
Week 4
£13,600
Week 5
£14,000
Week 6
£14,400
Week 7Large payment falls this week
£8,800
Week 8
£9,200
Week 9
£9,600
Week 10
£10,000
Week 11
£10,400
Week 12
£10,800
Week 13
£11,200

The low point is £8,800 in week 7, which stays above your floor of £5,000.

The useful action is usually to move the timing: bring receipts forward with deposits and faster invoicing, and push discretionary payments past the low week.

How to interpret the low point

The tool spreads typical weekly receipts and payments across the forecast, then places one lumpy payment in a selected week. It is a planning illustration, not a bank feed or a promise that receipts will arrive evenly.

Read the lowest projected balance first. Then replace the default assumptions with cleared-bank evidence, committed invoices and known tax, payroll, supplier and renewal dates. Test a downside receipt case rather than treating the average week as a safe amount.

  • Do not count an unapproved overdraft or hoped-for funding as available cash.
  • Use the linked scenario-planning guide when timing or receipt confidence is uncertain.
  • If the result shows an unsafe shortfall, the tool does not provide a credit application route.

Assumptions this tool makes

  • Receipts and payments are treated as level each week, which real businesses never are — use conservative receipt figures.
  • One lumpy payment (such as VAT, corporation tax or an annual insurance renewal) can be placed in a chosen week.
  • No interest, overdraft facility or credit line is assumed.

The formulas used

  • week_balance[w] = week_balance[w-1] + receipts - payments - (lumpy if w = lumpy_week)
  • low_point = minimum(week_balance[1..13])
  • weeks_of_cover = opening_balance / weekly_payments

Estimates only. This is a planning aid, not regulated financial advice, tax advice or a personal recommendation. Figures are rounded deliberately to avoid false precision. Your answers stay in your browser: nothing you type here is sent to us, to a partner or to an advertising platform. Read the full disclaimer.

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