Credit Card Interest Calculator
From balance, APR and monthly payment, compute the total interest paid while clearing the debt.
輸入資料
計算結果
重點速覽：Revolving credit-card interest accrues when you don't clear the balance in full within the grace period; the bank charges monthly on the outstanding amount. Declining-balance method: monthly interest = balance x APR/12; next balance = balance + interest - payment; sum of interest = total interest. HK credit-card APRs commonly exceed 30% — among the costliest borrowing; if payment ≤ first-month interest, the balance grows forever. WARNING: simplified model; actual interest differs with fees/rate changes. Education, not advice.
計算公式
每月利息 = 餘額 × APR ÷ 12。
每月餘額 = 餘額 + 每月利息 − 每月還款額。
總利息 = 逐月累加的所有利息，直至餘額歸零。
若每月還款額 ≤ 首月利息，則永遠無法還清 (月數顯示為 0)。
$$I_{t} = B_{t} \times \dfrac{\text{APR}}{12}, \qquad B_{t+1} = B_{t} + I_{t} - \text{Payment}$$$$\text{TotalInterest} = \sum_{t} I_{t} \quad (\text{直至 } B \le 0)$$使用說明
- Enter the current balance.
- Enter the APR.
- Enter the monthly payment to see total interest over repayment.
結欠 HK$50,000 於不同 APR 與每月還款額下的還清月數與總利息
| 每月還款 | APR 24% | APR 30% | APR 36% |
|---|---|---|---|
| HK$2,000 | 36 個月／息 HK$20,006 | 40 個月／息 HK$29,448 | 47 個月／息 HK$43,802 |
| HK$3,000 | 21 個月／息 HK$11,433 | 22 個月／息 HK$15,490 | 24 個月／息 HK$20,360 |
| HK$5,000 | 12 個月／息 HK$6,352 | 12 個月／息 HK$8,267 | 13 個月／息 HK$10,338 |
以結欠 HK$50,000、逐月遞減餘額法實算，數字四捨五入至整數。信用卡實際利息會因逾期費用、利率變動及最低還款隨餘額調整而不同，僅供參考。
理財情境案例
最低還款陷阱：HK$20,000 卡數竟要還逾 26 年
金管局「智醒消費者」以月息 2.5% (實際年利率約 35%) 示例，說明只還最低還款額的沉重代價。香港信用卡最低還款額一般為「所有利息及費用 + 至少 1% 未償還本金」，或某指定金額 (例如 HK$50) 取其高。
假設結欠 HK$20,000、APR 35%，若每月只還最低還款額 (利息 + 1% 本金)，還清竟需約 322 個月 (約 26.8 年)，累積利息高達約 HK$55,708——是本金的近 3 倍。這正是「最低還款陷阱」，務必盡量多還。
轉為低息貸款：把 30% 循環息換成 6% 私貸
以結欠 HK$50,000、APR 30%、每月還 HK$2,000 為例，需約 40 個月、付息約 HK$29,448。若把這筆卡數轉為年利率 6% 的私人貸款分 24 期償還，總利息可大幅降至約 HK$3,000 水平。
把高息卡數轉為低息個人貸款或利用免息結餘轉戶優惠期，是常見的減息策略。但要留意手續費、鎖定期及是否準時還款，避免優惠期後利率回升。
常見問題
How is credit card interest calculated?
Most cards charge monthly: monthly interest = outstanding balance x APR / 12. If not cleared in full within the grace period, the unpaid part accrues interest monthly and compounds.
How high is a Hong Kong credit card APR?
HK credit-card revolving APRs commonly exceed 30%; the HKMA example uses about 2.5% per month (~35% effective annual). Banks must disclose APR uniformly per the Code of Banking Practice. Although exempt from the moneylenders ordinance, rates should not be extortionate under the Code.
How is the minimum payment calculated, and what if I only pay it?
HK minimum payment is typically 'all interest and fees (incl. annual fee) + at least 1% of principal', or a fixed amount (e.g. HK$50), whichever is higher. Paying only the minimum avoids late fees but reduces principal extremely slowly, stretching repayment over decades with total interest multiple times the principal.
How can I reduce credit card interest?
Most effective: clear in full to use the interest-free period; if you can't, move the balance to a lower-rate personal loan or a 0% balance-transfer promo. Paying more each month also cuts total interest sharply.
Why can't the calculator show total interest?
When the monthly payment is ≤ the first month's interest, the balance grows instead of shrinking and interest accrues without limit — it can never be cleared. Raise the monthly payment above the interest to start reducing principal.
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。