FX Compound Interest Simulation: Monthly Return Scenarios and Realistic Cautions
Not sure how far compounding in FX can really grow your capital, or what a realistic number looks like?
In short, you can estimate it with principal x (1 + monthly return)^months, but the biggest pitfall is assuming the monthly return stays constant.
This article shows growth tables by monthly return and the recovery rate after losses. By the end, you can run a compounding estimate on sensible assumptions.
In short: FX compounding makes a big difference over time, but its assumptions break easily
- Compounding means adding profits to your principal and using them in the next trades
- Formula: principal x (1 + monthly return)^months. ¥100,000 at 3% for 12 months gives about ¥142,576 (hypothetical)
- Keeping the monthly return constant every month is hard, and the tables show an ideal case
- After a loss, recovery needs a higher gain than the percentage you lost
- Cashback gives back part of your cost and does not guarantee compounding
What is FX compounding? The difference from simple interest and the formula
Compounding means adding the funds you have gained to your principal and using that as the amount for the next period. In FX, this applies when you raise your lot size in line with your capital.
Simple interest keeps the principal fixed and grows by the same amount each month. With compounding, the monthly return also applies to the amount you gained, so the gap widens the longer the period.
| Item | Simple | Compound |
|---|---|---|
| Lot size | Stays the same | Increased in proportion to capital |
| Formula | Principal x (1 + monthly return x months) | Principal x (1 + monthly return)^months |
| ¥100,000, 3% monthly, 12 months | ¥136,000 | ¥142,576 |
| ¥100,000, 3% monthly, 36 months | ¥208,000 | ¥289,828 |
FX compound simulation: capital growth by monthly return
Starting from ¥100,000, we assumed monthly returns of 1%, 3% and 5% continue at a constant rate. Amounts are rounded.
| Monthly return | Calculation (12 months) | After 12 months | After 36 months |
|---|---|---|---|
| 1% | ¥100,000 x 1.01^12 | ¥112,683 | ¥143,077 |
| 3% | ¥100,000 x 1.03^12 | ¥142,576 | ¥289,828 |
| 5% | ¥100,000 x 1.05^12 | ¥179,586 | ¥579,182 |
Comparing with simple interest
Under the same assumptions, the gap from simple interest widens with longer periods and higher monthly returns. At a 1% monthly return over 12 months, the gap is ¥683.
| Monthly return | Simple, 12 months | Gap from compound | Simple, 36 months | Gap from compound |
|---|---|---|---|---|
| 1% | ¥112,000 | ¥683 | ¥136,000 | ¥7,077 |
| 3% | ¥136,000 | ¥6,576 | ¥208,000 | ¥81,828 |
| 5% | ¥160,000 | ¥19,586 | ¥280,000 | ¥299,182 |
Holding a 5% monthly return for three years is a level that is hard to maintain in practice. Do not be swayed by big numbers, and run your estimates with a lower monthly return.
FX compounding cautions: drawdowns and recovery rates
The growth tables assume the same monthly return every month. Actual results vary from month to month, and some months will be negative.
When capital shrinks, getting back to the original level needs a higher gain than the percentage you lost. This asymmetry is easy to overlook in compounding.
| Capital decline | Balance from ¥100,000 | Gain needed to recover |
|---|---|---|
| 10% | ¥90,000 | 11.1% |
| 20% | ¥80,000 | 25.0% |
| 30% | ¥70,000 | 42.9% |
| 50% | ¥50,000 | 100.0% |
The bigger the decline, the more sharply the burden of recovery grows. Money management that avoids large losses is what supports the assumptions behind compounding.
Raising lot size raises costs and losses too
- If you raise the lot size, the loss for the same pip range rises in proportion
- Trading costs such as spread also rise in proportion to lot size
- A losing streak at the increased lot size can cut capital sharply
- After profits, decide how much to raise your lot size with care
If 1 pip on USDJPY is roughly ¥1,000 per lot, a 20-pip loss on 0.1 lot is about ¥2,000. On 0.2 lot, it is about ¥4,000.
Thinking about FX compounding, cashback and tax
Cashback is a way of getting part of your cost back based on trading volume. It does not guarantee that your capital will grow through compounding.
Return amounts are not yet confirmed, and we will post them on each broker's page at launch. If you include them in a compounding calculation, use hypothetical values.
For residents of Japan, tax may apply to each year's profit. A pre-tax compounding calculation can look larger than reality. Treatment depends on your situation, so consult a specialist.
- Cashback is a way of getting part of your cost back, not a guarantee of profit
- Return amounts are not yet confirmed, so run estimates with hypothetical values
- Tax may apply each year, so pre-tax figures look larger than reality
Steps to use an FX compound simulation yourself
- 1
Set your starting capital
Use an amount kept separate from living expenses, one you could lose without affecting your life.
- 2
Set a modest monthly return
Use a figure lower than your past average, and compare returns around 1% and around 3%.
- 3
Allow for negative months
Include a case where capital falls 10-20% along the way, and check how many months recovery takes.
- 4
Subtract costs and tax
Review the result on a take-home basis after spread and tax.
Enter starting capital, monthly return and period to see capital growth under compound and simple interest.
Try the compound calculatorFAQ
Q.How much does ¥100,000 become at a 3% monthly return in FX?
In a hypothetical calculation, ¥100,000 x 1.03^12 gives about ¥142,576 after 12 months and about ¥289,828 after 36 months. There is no guarantee the monthly return can be held constant, so treat this as an estimate only.
Q.Is FX compounding realistic?
Holding a constant monthly return every month is hard, and losing months will occur. After a decline, recovery needs a large gain, so run estimates carefully with a lower monthly return and lot management.
Q.Which is better in FX, compound or simple interest?
If profits keep coming, compounding is better the longer the period. But losses also grow in proportion to lot size, so there is no general answer. Choose the one that suits your own money management.
This article is for information purposes only and is not investment advice. Conditions may change, so please check each broker's official page for the latest information. Offshore FX and CFD trading carries a risk of losses exceeding your principal.
