How Credit Card Interest Works
The Short Version
| Action |
Result |
| Pay full balance by due date |
$0 interest |
| Pay less than full balance |
Interest on entire balance |
| Pay only minimum |
Interest + lost grace period |
| Cash advance |
Interest from day 1 (no grace period) |
Interest Rates Explained
Types of Rates
| Rate Type |
Typical Range |
When It Applies |
| Purchase APR |
19.99-22.99% |
Carried balances |
| Cash advance APR |
22.99-27.99% |
ATM withdrawals, cash-like transactions |
| Balance transfer APR |
0-22.99% |
Transferred balances |
| Promotional APR |
0% |
Limited time offers |
| Penalty APR |
Up to 29.99% |
After missed payments (some issuers) |
Current Average Rates
| Card Type |
Typical Purchase Rate |
| Standard rewards |
19.99-20.99% |
| Premium rewards |
20.99-22.99% |
| Store credit cards |
25.99-29.99% |
| Low-interest cards |
8.99-12.99% |
| Student cards |
19.99% |
| Secured cards |
19.99% |
How Interest Is Calculated
Daily Interest Method
Canadian credit cards use daily compounding on the average daily balance:
| Step |
Formula |
| 1. Daily rate |
APR ÷ 365 |
| 2. Daily interest |
Average daily balance × daily rate |
| 3. Monthly interest |
Sum of all daily interest charges |
Example: $3,000 Balance at 19.99%
| Calculation |
Amount |
| Daily rate |
19.99% ÷ 365 = 0.05477% |
| Daily interest |
$3,000 × 0.0005477 = $1.64/day |
| Monthly interest |
~$1.64 × 30 = $49.28 |
| Annual interest |
$599.70 |
The Compounding Effect
Interest is charged on interest. A $3,000 balance left unpaid:
| Time |
Balance (Min Payments Only) |
Total Interest Paid |
| 1 year |
$2,530 |
$510 |
| 3 years |
$1,480 |
$1,280 |
| 5 years |
$750 |
$1,710 |
| Full payoff |
$0 (after ~15 years) |
$3,200+ |
Paying minimum only on $3,000 costs over $3,200 in interest — more than the original balance.
The Grace Period
What It Is
The grace period is the time between your statement date and payment due date — typically 21-25 days.
| Scenario |
Grace Period Active? |
Interest Charged? |
| Paid last month in full |
✅ Yes |
No interest |
| Carried a balance last month |
❌ No |
Interest from purchase date |
| Cash advance |
❌ Never |
Interest from transaction date |
How to Keep Your Grace Period
Statement closes → 21-25 day grace period → Due date
↓
Pay FULL balance here = $0 interest next month
Pay LESS than full = lose grace period on NEW purchases
Critical point: If you carry even $1 of balance past the due date, you lose the grace period and new purchases accrue interest immediately.
Minimum Payments
How Minimums Are Calculated
| Issuer |
Minimum Payment Formula |
| Most banks |
Greater of: $10 or 2-3% of balance |
| Some issuers |
Greater of: $10 or 1% of balance + interest |
The Minimum Payment Trap
$5,000 balance at 19.99%, paying only minimums:
| Month |
Payment |
Interest |
Applied to Balance |
Remaining |
| 1 |
$100 |
$83 |
$17 |
$4,983 |
| 12 |
$93 |
$78 |
$15 |
$4,660 |
| 60 |
$68 |
$52 |
$16 |
$3,110 |
| 180 |
$21 |
$3 |
$18 |
$170 |
Time to pay off: ~22 years
Total interest: ~$7,700
Cash Advances
Why They’re Expensive
| Feature |
Regular Purchases |
Cash Advances |
| Grace period |
21-25 days |
None |
| Interest rate |
19.99% |
22.99-27.99% |
| Interest starts |
After due date (if unpaid) |
Immediately |
| Additional fee |
None |
3-5% of amount |
What Counts as Cash Advance
| Transaction |
Cash Advance? |
| ATM withdrawal with credit card |
✅ Yes |
| Wire transfers |
✅ Yes |
| Casino purchases |
✅ Yes |
| Crypto purchases |
✅ Yes |
| Gift card purchases (sometimes) |
⚠️ Varies |
| Online bill payments from credit card |
⚠️ Varies |
How to Avoid Paying Interest
Strategy 1: Pay in Full Every Month
| Month |
Statement Balance |
You Pay |
Interest |
| January |
$2,000 |
$2,000 |
$0 |
| February |
$1,800 |
$1,800 |
$0 |
| March |
$2,200 |
$2,200 |
$0 |
Result: You use the bank’s money for 21-45 days free.
Strategy 2: Pay Before Statement Closes
Paying before your statement closes reduces your reported balance, which also helps your credit utilization ratio.
Strategy 3: If You Must Carry a Balance
- Use a low-interest card (8.99-12.99%) for the carried balance
- Use a rewards card (paid in full) for daily purchases
- Consider a balance transfer at 0% to pay down faster
Interest Costs at Different Rates
Monthly cost of carrying various balances:
| Balance |
8.99% |
12.99% |
19.99% |
22.99% |
| $1,000 |
$7.49 |
$10.83 |
$16.66 |
$19.16 |
| $3,000 |
$22.48 |
$32.48 |
$49.98 |
$57.49 |
| $5,000 |
$37.46 |
$54.13 |
$83.29 |
$95.79 |
| $10,000 |
$74.92 |
$108.25 |
$166.58 |
$191.58 |