What happens if you invest $100 a month?
Putting $100.00 a month aside grows to $1,245 in a year and $18,289 after 10 years at 8.0% APR. That is about 2.3 reliable used cars.
The numbers
Timeline: what happens, and when
- Day 1$3.29
You have invested $3.29.
- After 1 week$23.01
You have invested $23.01.
- After 1 month$98.63
You have invested $98.63.
- After 3 months$298
You have invested $296. Compounding at 8.0% has added $1.93 on top, for a balance of $298 — about 5.0 months of streaming services.
- After 6 months$602
You have invested $592. Compounding at 8.0% has added $9.78 on top, for a balance of $602 — about a new smartphone.
- After 1 year$1,245
You have invested $1,200. Compounding at 8.0% has added $44.96 on top, for a balance of $1,245 — about 3.1 new smartphones.
- After 3 years$4,053
You have invested $3,600. Compounding at 8.0% has added $453 on top, for a balance of $4,053 — about 2.4 months of median US rent.
- After 5 years$7,347
You have invested $6,000. Compounding at 8.0% has added $1,347 on top, for a balance of $7,347 — about 4.3 months of median US rent.
- After 10 years$18,289
You have invested $12,000. Compounding at 8.0% has added $6,289 on top, for a balance of $18,289 — about 2.3 reliable used cars.
What this actually means
The habit is small. The total is not.
$3.29 a day feels like nothing — it is about 1.6 months of streaming services a month. But run it for 10 years and it becomes $18,289, which is about 2.3 reliable used cars.
Interest does the second half of the work
Of that $18,289, you personally put in $12,000. The remaining $6,289 came from interest — money you did not earn by working.
What one skipped day costs you
Skipping a single $3.29 deposit today costs you $7.10 ten years from now. Skipping one day a week costs you $2,604 over a decade.
What if you changed the number?
Same habit, different size. Each one is a full simulation of its own.
Try a different time frame
Frequently asked questions
How much is $100.00 a month in a year?
You contribute $1,200 over 12 months. With interest at 8.0% APR compounded monthly, the balance reaches about $1,245.
What if I keep going for 10 years?
Ten years of $3.29 a day is $12,000 contributed and about $18,289 in total — about 2.3 reliable used cars.
How long until I have $1,000?
At $3.29 a day you cross $1,000 on day 305 — about 10.0 months in. $10,000 takes about 8.3 years.
Is 8.0% a realistic return?
It is the long-run average of a broad stock index after inflation-adjusted dividends are reinvested. Real years swing from -30% to +30%; the average only shows up over decades.
Assumptions behind these numbers
- Assumes 8.0% annual return compounded monthly and no withdrawals.
- Figures are nominal — they ignore inflation, taxes on interest, and fees.