The runway number on your dashboard is the most-watched figure in ReservWise. It answers a single question: if no new money arrived starting today, how many weeks could you keep the lights on? Most operators glance at it before every spending decision over $200. Knowing how it is built makes it trustworthy.
The formula
Runway, in weeks, is computed as:
runway_weeks = available_cash / weekly_essential_burnThat is the headline math. Two terms do real work:
- available_cash = current liquid balances + protected reserve balances above their floors, minus tax pre-skim already owed.
- weekly_essential_burn = trailing 90-day average of expenses tagged as Survival or Business Ops, divided by 13.
The forecast also computes a projected runway that adds weighted expected income to the numerator. Both numbers show up on the chart — the lower one (today's true runway) is the headline, the upper one (projected) is the dashed line.
What counts as available cash
Cash you can actually reach in the next 7 days, without taking on debt:
- Operating checking + savings balances synced via Plaid.
- Reserve balances above their floors. The portion below the floor is treated as untouchable.
- Confirmed deposits in transit (already invoiced and acknowledged).
What does not count:
- Money in Tax Reserve. The IRS owns it — you are just holding it.
- Investment / brokerage balances. Liquidating takes days and tax events.
- Credit-card limits. Capacity is not cash.
- Likely or Speculative income. Those flow into the projected runway, not today's.
How weekly burn is computed
ReservWise looks at the trailing 90 days of expenses, filters to those tagged Survival or Business Ops, sums them, and divides by 13 weeks. The answer is your weekly essential burn.
Three things you can override in Settings → Forecasting → Burn calculation:
- Window length — switch from 90 to 30 or 180 days. Shorter windows react faster to recent changes; longer windows smooth out one-off months.
- Categories included — by default Survival + Business Ops only. You can add Tax (counts the pre-skim as essential) or include Growth if you treat your subscription tools as non-negotiable.
- One-off exclusion — flag transactions over a threshold as one-time so they do not inflate the average. Useful after a big annual insurance renewal.
A worked example
Operator has:
- Operating checking: $8,200
- Survival reserve: $6,000 (floor: $4,000) → $2,000 above floor counts
- Business Ops reserve: $3,400 (floor: $3,000) → $400 above floor counts
- Tax Reserve: $5,200 → does not count
- One confirmed invoice in transit: $2,800
available_cash = 8,200 + 2,000 + 400 + 2,800 = $13,400
Trailing 90-day Survival + Business Ops expenses: $13,650
weekly_essential_burn = 13,650 / 13 = $1,050 / week
runway_weeks = 13,400 / 1,050 = ~12.8 weeks
That is the headline number. If the operator also has $4,200 of Likely + Speculative income weighted to $2,940, the projected runway extends to roughly 15.6 weeks — the dashed line on the chart.
Overrides you can make
Most operators leave the defaults alone for the first few months. Once you have data, the levers worth tuning:
- Confidence weights for projected income (default 70% / 30% for Likely / Speculative).
- Burn window if recent months have been atypical.
- Floor overrides per reserve — if you treat a reserve as untouchable beyond the floor, mark it locked and the surplus stops counting as available.
What the runway number is telling you
- Under 4 weeks — danger zone. Pause discretionary spending. Consider Lean Month Mode. Surface Survival shortfalls to AI Coach.
- 4–12 weeks — normal operating range for many variable-income operators. Watch the trend line; the absolute number matters less than whether it is rising or falling week over week.
- 12–26 weeks — comfortable. Time to grow Wealth Building or Growth allocations.
- 26+ weeks — strong. If you have been here for 3+ months, look at deploying capital — your reserves may be over-funded relative to your real volatility.
Common mistakes to avoid
- Counting Tax Reserve as runway. It is not yours. Treating it as runway is how operators end up under-paying quarterly estimates.
- Trusting projected runway as headline. The dashed line is hopeful. The solid line is the truth. Make decisions against the solid line.
- Shrinking the burn window to make the number look better. Shorter windows are not lying — they are just more reactive. Use them when something real has changed, not when you want a prettier chart.
- Ignoring trend. A flat 8-week runway is fine. An 8-week runway that was 14 weeks a month ago is a signal.
What to do next
- Open the dashboard and hover the runway chart — you will see the breakdown of available_cash and weekly_burn for that week.
- Read Reading the runway forecast chart for the visual conventions.
- Read Logging speculative income with confidence levels for how the projected line is built.
- If your headline runway feels wrong, check Settings → Forecasting and verify your burn window and category inclusions.
Runway is the floor under your spending decisions. Knowing how it is built makes the floor solid instead of suspicious.