Weekly Compound Interest Calculator
Weekly compounding sits between monthly and daily compounding. The main question is not whether it is better. It is whether the difference is large enough to matter in your real plan.
What to watch for
- Frequency changes are usually a second-order effect.
- Time horizon and contribution size usually dominate the outcome.
- Weekly compounding can still be useful when comparing account products with similar rates.
Practical use case
If two products offer nearly the same annual rate, then compounding frequency can help break the tie. If one product has a meaningfully higher rate, the rate usually matters more than whether it compounds weekly or monthly.
Related pages
What weekly compounding is actually worth
Weekly compounding is rare as a product feature but common as a question, usually from people paid weekly who want to model deposits on the same cycle. The comparison below holds everything constant except the frequency: $10,000 at a 6% nominal rate for 10 years, with no contributions.
| Compounded | Periods per year | Balance after 10 years | Effective annual rate |
|---|---|---|---|
| Yearly | 1 | $17,908.48 | 6.0000% |
| Quarterly | 4 | $18,140.18 | 6.1364% |
| Monthly | 12 | $18,193.97 | 6.1678% |
| Weekly | 52 | $18,214.89 | 6.1800% |
| Daily | 365 | $18,220.29 | 6.1831% |
| Continuously | ∞ | $18,221.19 | 6.1837% |
The final row is the mathematical ceiling. No compounding schedule can beat continuous compounding.
Weekly compounding beats yearly compounding by about $306.41 over the decade — real money. But it beats monthly compounding by only $20.92. Nearly all of the benefit of compounding more often is captured by the time you reach monthly; everything after that is a rounding error dressed up as a feature.
The practical consequence is that compounding frequency is close to the least important thing to compare between two savings products. The rate matters enormously, fees matter enormously, access conditions matter. Whether interest is applied 12 or 365 times a year does not.
Where frequency does start to matter
- On borrowing. The same arithmetic runs against you. Credit card interest compounded daily on a revolving balance is materially worse than the quoted annual rate suggests.
- At high rates. The gap between frequencies widens as the rate rises. At 6% the annual-to-daily gap is small; at 20% it is not.
- When comparing quoted rates. A nominal rate compounded daily and a nominal rate compounded annually are not comparable. Convert both to an effective annual rate first — the EAR calculator does it in one step.
- Never for contribution timing. How often you deposit is a separate question from how often interest is applied, and confusing the two is the most common error in this area.
The compounding frequency guide works through the full comparison, including why the effective rate converges rather than growing without limit.
Questions about weekly compounding
How do I calculate weekly compound interest?
Divide the annual rate by 52 and apply it 52 times a year: FV = P × (1 + r/52)52t. On $10,000 at 6% for 10 years that gives $18,214.89.
Is weekly compounding much better than monthly?
No. On these inputs the difference over 10 years is about $20.92 — roughly 0.21% of the starting balance. The rate is worth far more attention.
Does the frequency change how much I should contribute?
No. Contribution size and timing are independent of how often interest is applied. Deposit on whatever schedule matches your income; the frequency of compounding is the account's business, not yours.