13-Week Cash Flow Forecaster
The distressed-M&A standard for short-term liquidity, applied to startups and growth-stage businesses. Models 13 weeks of inflow and outflow, AR/AP timing, four seasonality patterns, and fires a runway alarm when ending balance dips below your safety floor. Presets from Pavilion 2024, Bessemer Cloud Index, Shopify Plus, SPI Research, and a16z.
Quick Conversion
Formula: Monthly = Weekly × 4.333
Industry presets — Pavilion 2024 anchors
Pavilion 2024 startup cash report: Series A SaaS median DSO 38 days, monthly burn $580K-$680K. 6-quarter runway is the board minimum, with 4 quarters the trigger for bridge talks.
Inputs
13-Week Cash Flow Strip
Green = weekly inflow. Red = weekly outflow. Sky-blue line = ending cash balance. Red dashes = safety floor. Red dots = weeks below floor.
Week-by-week forecast (live)
| Week | Inflow | Outflow | Net | Ending | vs floor |
|---|---|---|---|---|---|
| W1 | $220,000 | $360,000 | -$140,000 | $6,360,000 | $4,860,000 |
| W2 | $220,000 | $360,000 | -$140,000 | $6,220,000 | $4,720,000 |
| W3 | $220,000 | $360,000 | -$140,000 | $6,080,000 | $4,580,000 |
| W4 | $220,000 | $360,000 | -$140,000 | $5,940,000 | $4,440,000 |
| W5 | $220,000 | $360,000 | -$140,000 | $5,800,000 | $4,300,000 |
| W6 | $220,000 | $360,000 | -$140,000 | $5,660,000 | $4,160,000 |
| W7 | $220,000 | $360,000 | -$140,000 | $5,520,000 | $4,020,000 |
| W8 | $220,000 | $360,000 | -$140,000 | $5,380,000 | $3,880,000 |
| W9 | $220,000 | $360,000 | -$140,000 | $5,240,000 | $3,740,000 |
| W10 | $220,000 | $360,000 | -$140,000 | $5,100,000 | $3,600,000 |
| W11 | $220,000 | $360,000 | -$140,000 | $4,960,000 | $3,460,000 |
| W12 | $220,000 | $360,000 | -$140,000 | $4,820,000 | $3,320,000 |
| W13 | $220,000 | $360,000 | -$140,000 | $4,680,000 | $3,180,000 |
Formula Card
Net Burn = Outflow - Inflow (per week, per month)Runway (months) = Opening Cash / Monthly Net BurnEnding Balance(W_n) = Opening + sum(Inflow_i - Outflow_i) for i = 1..nSeasonalised Inflow(W_n) = Base Inflow × Season_factor(n)Safety Floor breach: Ending Balance(W_n) < Safety FloorWorked: opening $6.5M, weekly inflow $220K (flat seasonality), weekly outflow $360K - net burn $140K/wk × 4.333 = $607K/mo. Runway = 6.5M / 607K = 10.7 months. Safety floor $1.5M is breached at week 36 - outside the 13-week window but inside next-quarter view.
Saved snapshots
No snapshots yet. Run weekly to track variance.
How to build a 13-Week Forecast
- Pull opening cash from the bank balance - not the GL. Direct method only works with actual cash.
- Compute average weekly inflow from rolling 4-week receipts (cash, not invoiced).
- Compute average weekly outflow from rolling 4-week disbursements + payroll dates within the window.
- Pick the seasonality shape closest to your domain - flat for B2B SaaS, Q4 for DTC, summer for camps/services, spring for tax-prep.
- Set safety floor = 3-6 months of opex per Bessemer guidance. Re-run weekly; replace forecast with actuals.
A Brief History of 13-Week Cash Forecasting
In 2026, a SaaS CFO carrying 9 months of runway needs a 13-week cash forecast that flags the week the bank balance dips below safety floor - before the board, the auditor, or the bank does. The 13-week cash forecast was formalised by distressed-M&A teams at Alvarez & Marsal, AlixPartners, and FTI Consulting in the 1990s as the operational standard for liquidity management. It has since been adopted by every well-run finance team, from pre-seed startups to Fortune 500 treasury.
The direct-method forecast (used by this tool) tracks actual cash receipts and disbursements by week, rather than backing into cash from net income. Direct method is the global treasury standard (AFP Treasury Foundation 2023, EuroFinance Cash Pulse 2024). The advantage is precision at short horizons; the cost is more granular inputs. The tool here splits inflows into receivables (AR-aged), recurring revenue (subscriptions, retainers), and one-off events, and outflows into payroll, vendor, debt service, and one-off events.
Pavilion's 2024 State of Startup Finance (David Politis, Sam Jacobs) surveys 2,200 startup finance leaders and reports: median DSO 38 days for SaaS, 52 days for services, 14 days for marketplaces, near-zero for DTC. Median monthly burn for Series A SaaS is $580K-$680K; Series B is $1.2M-$1.8M. Cash safety floor (minimum operational balance) for SaaS is typically 3 months of opex; for fintech with regulatory capital, 6 months.
Bessemer State of the Cloud has tracked SaaS runway over the past five years and reports a steady tightening: 2021 median runway was 22 months at the median Series A, 2024 median is 14 months. The squeeze is partly the 2022-23 venture funding contraction, partly higher cloud and salary base costs. The runway alarm in this tool defaults to the Bessemer 'tight' threshold of 12 months.
Seasonality is the second-most-common forecast error after DSO. Shopify Plus 2025 reports that Q4 (Oct-Dec) accounts for 35-45% of annual revenue for established DTC brands; SPI Research 2025 reports services see a summer dip; tax-prep fintech (Intuit, H&R Block) compresses 60-70% of revenue into Jan-April. The seasonality dial here scales weekly inflows so the 13-week forecast reflects reality, not a flat extrapolation.
Distressed-M&A practice (A&M's 13-week forecast manual, 2021) recommends a 5% variance tolerance at week 4 and 15% at week 13. Startups widen this to 10-25% because revenue is harder to predict, but the discipline - weekly update, actuals replacing forecasts, variance bridge - is the same. The tool here writes snapshot history to localStorage for week-on-week variance review.
Modern AR/AP automation tools (Tesorio, Versapay, Stampli, Routable, BILL) compress DSO by 4-9 days on average (Pavilion 2024 case studies) and stretch DPO by 3-6 days. Each day of DSO compression releases roughly one day of revenue from AR; the working-capital release scales linearly with revenue. The 13-week forecast here lets you slide DSO and DPO independently and watch the ending balance and runway respond.
Trusted by CFOs, treasurers, and fractional finance leads
“I run this against every portfolio company before board meetings. The seasonality dial + runway alarm caught a Q4 cash crunch for one of my DTC clients eight weeks early. Bought us time to factor AR.”
“Settlement timing was the killer. The DSO/DPO arrows on the strip showed we had a 7-day float problem hiding our true burn. Fixed payment cadence, runway went from 11 to 16 months on the same revenue.”
“Replaced our Sheets-based 13-week with this. The Pavilion preset matched our actuals within 8% and the safety-floor logic flagged the reserve requirement our auditor had been nagging about.”
“Best part is the explicit AR and AP timing — it stopped my CEO from confusing recognised revenue with cash. The runway alarm gives a single, defensible number for fundraising conversations.”
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