Average Propensity to Consume (APC) Calculator
From total consumption and disposable income, compute the average propensity to consume (APC), average propensity to save (APS) and amount saved.
輸入資料
計算結果
重點速覽：APC = total consumption / disposable income. APS = 1 - APC. APC between 0 and 1 means saving; =1 break-even; >1 dissaving (borrowing). APC looks at the whole (average); MPC looks at the incremental. Low-income households tend to have higher APC.
計算公式
平均消費傾向 APC = 總消費 ÷ 可支配收入。
平均儲蓄傾向 APS = 1 − APC。
未消費金額 = 可支配收入 − 總消費。
$$APC = \dfrac{Consumption}{DisposableIncome}$$$$APS = 1 - APC$$使用說明
- Enter total consumption for the period.
- Enter disposable (after-tax) income for the same period.
- View APC, APS and the amount not consumed.
可支配收入 15,000 下,不同消費水平對 APC、APS 與未消費金額的影響
| 總消費 (HK$) | 可支配收入 (HK$) | APC | APS | 未消費金額 (HK$) |
|---|---|---|---|---|
| 12,000 | 15,000 | 0.800 | 0.200 | 3,000 |
| 13,500 | 15,000 | 0.900 | 0.100 | 1,500 |
| 15,000 | 15,000 | 1.000 | 0.000 | 0 |
| 16,500 | 15,000 | 1.100 | −0.100 | −1,500 |
APC 隨消費佔收入比例上升而增大。APC = 1 表示收支相抵、無儲蓄;APC > 1 (如 1.1) 表示入不敷支,需動用過往儲蓄或借貸支撐,此時 APS 為負。
理財情境案例
案例一：由月收支計算 APC 與 APS
某人某月可支配收入 (稅後) 15,000 元,總消費 12,000 元,想了解自己的消費與儲蓄結構。
APC = 總消費 ÷ 可支配收入 = 12,000 ÷ 15,000 = 0.8,代表 80% 的收入用於消費。APS = 1 − 0.8 = 0.2,即 20% 存起;未消費金額 = 15,000 − 12,000 = 3,000 元。
APC = 0.8 屬健康水平 —— 消費低於收入、有兩成儲蓄,能累積應急資金與投資本錢。一般建議至少維持正儲蓄 (APC < 1),並視情況把 APS 目標訂在 0.1 至 0.2 以上。
案例二：APC 超過 1 的警號
延伸:若同一個月因大額支出 (如置裝、旅遊、突發醫療),消費升到 16,500 元,但收入仍是 15,000 元。
APC = 16,500 ÷ 15,000 = 1.1,APS = 1 − 1.1 = −0.1 (負儲蓄);未消費金額 = 15,000 − 16,500 = −1,500 元 —— 即入不敷支 1,500 元,需靠動用過往儲蓄、信用卡借貸或一次性資金支撐。
偶爾一個月 APC > 1 (如遇大額支出) 屬正常;但若『長期』APC 持續 ≥ 1,代表消費結構性地超過收入,儲蓄被侵蝕、債務可能累積,需認真檢視預算與消費習慣。實務提醒:(1) 分子分母要同期、同口徑,且用稅後可支配收入;(2) 一次性大額支出宜攤到較長期間看,避免單月失真;(3) APC 看整體結構,想看『加薪後會多花多少』要用 MPC。可搭配本站『邊際消費傾向 (MPC)』『訂閱浪費』等計算器管理消費。本工具僅供教學估算,不構成理財建議。
常見問題
How is APC different from MPC?
APC is the share of total disposable income spent; MPC (marginal propensity to consume) is how much of an extra dollar of income is spent. You might spend 70% of your income overall (APC 0.7) but only 40% of a raise (MPC 0.4).
Why use disposable rather than pre-tax income?
APC measures how freely-available income is split between consumption and saving, so the denominator should be after-tax disposable income. Using pre-tax income understates APC and breaks comparability.
What does APC > 1 mean?
It means consumption exceeds disposable income — dissaving. Usually funded by drawing down savings, credit cards or one-off spending. Occasional spikes are normal; sustained dissaving needs budget review.
What is a healthy APC?
APC has no absolute 'good' value. The basic floor is APC < 1 (positive saving). A common personal-finance target is a 10-20% saving rate (APC about 0.8-0.9 or lower); the 50/30/20 rule suggests 20% to saving/debt. Low-income households naturally have higher APC due to essential costs — judge by income level and life stage, not a single number.
Why is APC usually greater than MPC?
Keynes's consumption function: consumption = autonomous consumption + MPC x income. Autonomous consumption is a 'floor' (basic spending even at zero income) that lifts the average (APC) above the slope (MPC). As income rises, the fixed floor is spread thinner, so APC falls toward MPC. This is why low-income APC is high and high-income APC is low.
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。