Defensive Interval Ratio (DIR) Calculator
From liquid assets and annual operating expenses, compute the defensive interval (in days) — how long a firm survives with no new revenue.
輸入資料
計算結果
重點速覽：DIR = liquid assets / daily operating expense; daily = annual operating expenses / 365 (exclude depreciation/amortisation, non-cash). Liquid assets = cash, equivalents, short-term investments, receivables (exclude inventory, prepaid). Example: 600k liquid, 1.46m annual → daily 4,000, DIR 150 days (~5 months). More days = thicker buffer. WARNING: Zero-revenue stress test; compare with quick/current ratio and cash flow. Education, not advice.
計算公式
每日營運支出 = 每年營運支出 ÷ 365。
防禦區間比率 (天數) = 速動資產 ÷ 每日營運支出。
$$\text{Daily Operating Expenses} = \dfrac{\text{Annual Operating Expenses}}{365}$$$$\text{Defensive Interval Ratio (days)} = \dfrac{\text{Liquid Assets}}{\text{Daily Operating Expenses}}$$使用說明
- Enter liquid assets (cash, short-term investments, receivables).
- Enter annual cash operating expenses (exclude depreciation).
- View the days the firm can operate with no new revenue.
以每年營運支出固定為 HK$1,460,000 (每日 HK$4,000) 為例，速動資產由 HK$365,000 增至 HK$1,095,000 時的防禦區間天數變化，說明可變現資產如何決定生存續航力。
| 速動資產 (HK$) | 每日營運支出 (HK$) | 防禦區間 (天數) | 約相當於 |
|---|---|---|---|
| 365,000 | 4,000 | 91 天 | 約 3 個月 |
| 600,000 | 4,000 | 150 天 | 約 5 個月 |
| 730,000 | 4,000 | 183 天 | 約半年 |
| 1,095,000 | 4,000 | 274 天 | 約 9 個月 |
理財情境案例
個案一：初創公司的『燒錢跑道』
一間香港初創科技公司仍在燒錢階段：手上速動資產 (現金加約當現金) 為 HK$2,400,000，每年現金營運支出 (主要為薪資與租金) 約 HK$7,300,000，即每日約 HK$20,000。
DIR = 2,400,000 ÷ 20,000 = 120 天，代表若下一輪融資或收入遲遲未到，公司靠現有現金約可再撐 4 個月。這正是創投圈常說的『資金跑道 (runway)』概念 — 對尚未盈利的初創而言，DIR (跑道天數) 比任何盈利比率都更攸關生死，管理層須密切監控，並在跑道耗盡前完成融資或達到收支平衡。
個案二：季節性生意的淡季緩衝
一間主打聖誕與農曆新年旺季的香港禮品貿易公司，全年營運支出 HK$1,460,000 (每日 HK$4,000)，淡季期間幾乎沒有新訂單收入。旺季結束後，它手上速動資產為 HK$600,000。
DIR = 600,000 ÷ 4,000 = 150 天 (約 5 個月)，剛好足以覆蓋數月的淡季營運，撐到下一個旺季來臨。這說明季節性行業不能只看年度平均，更要用 DIR 檢視『淡季零收入時能撐多久』；若 DIR 短於淡季長度，公司就必須預留信貸額度或提前備妥現金，否則會在淡季中段出現資金缺口。
常見問題
How is DIR different from quick and current ratios?
Quick/current ratios divide assets by liabilities (a multiple, measuring debt coverage). DIR divides liquid assets by daily operating expense, giving days of survival with zero revenue (resilience). Example: a quick ratio of 1.2 says little about endurance, but DIR of 150 days directly shows the buffer against income interruption. Use all three: quick/current for debt structure, DIR for worst-case survival.
Why exclude depreciation and amortisation?
DIR measures how long real cash can fund operations. Depreciation/amortisation are non-cash accounting charges — no actual cash leaves. Including them overstates daily cash burn and understates survival days. Enter cash operating expenses only (wages, rent, utilities, materials, interest).
Is more days always better?
Generally more days = stronger resilience, valuable in recessions or crises. But too long may signal idle cash and poor capital efficiency (lower returns). 'Safe' depends on industry and revenue stability: stable cash flows (utilities) need less; volatile/seasonal firms need more. Read with trend and peers.
What are liquid assets, and what to include?
Liquid (defensive) assets are those quickly convertible to cash: cash & equivalents, short-term investments (marketable securities, money-market funds), and accounts receivable. Exclude inventory (slow to realise) and prepaid expenses (already paid). Watch receivables quality — large bad debts reduce realisable liquid assets below book.
Which companies is DIR most useful for?
Those where cash endurance is existential: (1) pre-profit startups — DIR is their 'runway' before the next raise; (2) seasonal/volatile industries (travel, retail, F&B, trading) — checks off-season survival; (3) firms in crisis/turnaround — assesses short-term buffer; (4) stress testing even stable firms. For stable mature firms (utilities, steady REITs), DIR is less critical; profitability and leverage matter more. Always pair with quick ratio, current ratio and operating cash flow.
相關工具
參考資料
內容審核：香港計算器財經團隊。計算邏輯與公式參考香港金融管理局（HKMA）及投資者及理財教育委員會（IFEC）之個人理財計算指引，結果僅供參考，實際以相關機構公佈為準。