Buying Power Calculator
From cash, margin multiplier and unrealised P/L, compute your available buying power for trading.
輸入資料
計算結果
重點速覽：Buying power is the maximum market value you can buy in a brokerage account. buying power = (cash + unrealised P/L) x margin multiplier. Example: cash 100k, 4x, no P/L → 400k; if you already hold 100k of margin stock, available = 400k - 100k = 300k. Margin amplifies gains AND losses; a margin call can force liquidation in a downturn. In Hong Kong, securities margin is subject to SFC and exchange rules (e.g. 50% initial margin for many positions); broker terms vary. Estimate only, not advice.
計算公式
等值購買力 = 名目金額 × (基期 CPI ÷ 現期 CPI)。
$$等值購買力：$PP = Amount \times \dfrac{CPI_{base}}{CPI_{current}}$$$$$其中 $Amount$ 為名目金額、$CPI_{base}$ 為基期物價指數、$CPI_{current}$ 為現期物價指數。$$$$示例：$1{,}000 \times \dfrac{100}{120} \approx 833.33$$$使用說明
- Enter the cash balance and the margin multiplier.
- Enter any unrealised P/L on open positions.
- View the available buying power.
名目 HK$1,000 (基期 CPI = 100) 在不同現期物價水平下的等值購買力
| 現期 CPI | 物價漲幅 | 等值購買力 (HK$) | 被侵蝕價值 (HK$) |
|---|---|---|---|
| 110 | +10% | 909.09 | 90.91 |
| 120 | +20% | 833.33 | 166.67 |
| 150 | +50% | 666.67 | 333.33 |
| 200 | +100% | 500.00 | 500.00 |
理財情境案例
案例一：換算今天 1,000 元的等值購買力
假設某商品籃子在基期時物價指數為 100，如今物價上漲至指數 120 (即整體物價比基期漲了 20%)。想知道今天的 HK$1,000，相當於基期時多少購買力。
等值購買力 = 1,000 × (100 ÷ 120) ≈ HK$833.33。
解讀：今天的 HK$1,000，只相當於基期時 HK$833.33 的購買力——通脹在這段期間侵蝕了約 HK$166.67 的實質價值。錢的『數字』沒變，但它能換到的『實質東西』少了。理解這一點，才能避免被表面的名目金額誤導。
案例二：加薪到底有沒有跑贏通脹？
王先生十年前月薪 HK$20,000 (當時 CPI = 100)，如今月薪加到 HK$24,000 (現時 CPI = 130)。表面看加薪了 20%，但實質上真的變富了嗎?
把今天的 HK$24,000 用基期物價換算：24,000 × (100 ÷ 130) ≈ HK$18,461.54。與十年前的 HK$20,000 相比，實質購買力反而下降了約 (18,461.54 − 20,000) ÷ 20,000 ≈ −7.69%。
解讀：雖然名目薪資漲了 20%，但同期物價漲了 30%，換算成實質購買力後，王先生其實比十年前更『買不起東西』了——名目加薪、實質變窮。這說明評估收入是否真正提升，必須用購買力換算成同一物價基準來看，而不是只看帳面數字。本站另有通脹相關計算器可搭配使用。
常見問題
What is buying power?
The maximum market value you could buy in the account with your cash and margin. With a 4x multiplier, HK$100,000 cash gives HK$400,000 of buying power. It shows spare capacity and the leverage you carry.
How does margin multiply risk?
Margin lets you control more than your cash; gains and losses are both magnified versus the cash put in. A small adverse move can blow up the loss ratio and trigger a margin call — the broker demands more cash or sells your holdings, possibly at the worst time. Use leverage with strict risk control.
What is a margin call?
When your equity falls below the maintenance requirement (after losses), the broker asks you to top up cash or close positions. If you cannot, it liquidates — often locking in losses. Keep a buffer and never run buying power to the limit.
Does Hong Kong regulate margin?
Yes. Hong Kong securities margin trading is supervised by the SFC and exchanges; many stock positions require a 50% initial margin (2x) and a maintenance level. Leveraged FX/commodity products may have stricter or different rules. Broker terms differ — read your agreement.
How does this relate to day-trading buying power?
Some markets allow intraday 4x for pattern day traders; the principle is the same (multiplier times cash), but it may only apply to positions closed same day. This tool uses the multiplier you enter; set it per your account and product rules.
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。