Investing math is mostly multiplication repeated over time, and trading math is mostly division by risk. Both are easy to get wrong in your head and slow to set up in a spreadsheet. This calculator for investors and traders puts the rate, the horizon and the stop on their own named lines, so you can try a different assumption by changing one number.
The examples show the answers Notes Calculator gives with made-up figures. Choose Open in Notes Calculator to open one in the web app and use your own.
Compound growth over 30 years
Raise one plus the yearly rate to the number of years and multiply by the starting balance.
| Note | Result |
|---|---|
| principal = 10k USD | $10,000 |
| rate = 7% | 7% |
| After 30 years: principal * (1 + rate) ^ 30 | $76,122.55 |
| Years to double, Rule of 72: 72 / 7 | 10.29 |
The Rule of 72 is a shortcut: divide 72 by the yearly rate in percent for a rough doubling time.
Monthly contributions
For a fixed deposit every month, the future value uses the monthly rate and the number of months. Compare it with what you put in to see how much came from growth.
| Note | Result |
|---|---|
| deposit = 500 USD | $500 |
| rate = 7% | 7% |
| periods = 20 * 12 | 240 |
| Future value: deposit * ((1 + rate / 12) ^ periods - 1) / (rate / 12) | $260,463.33 |
| Deposited: deposit * periods | $120,000 |
Position size from risk per trade
Decide how much of the account you will risk, turn it into a dollar amount, and divide by the distance to your stop. The result is a share count.
| Note | Result |
|---|---|
| account = 20,000 USD | $20,000 |
| entry = 180 USD | $180 |
| stop = 172 USD | $172 |
| risk amount = account * 1% | $200 |
| shares = risk amount / (entry - stop) | 25 |
| Position value: shares * entry | $4,500 |
Reward to risk
Before you enter, compare the distance to your target with the distance to your stop.
| Note | Result |
|---|---|
| entry = 180 | 180 |
| stop = 172 | 172 |
| target = 204 | 204 |
| Reward to risk: (target - entry) / (entry - stop) | 3 |
A running profit and loss
Label each closed trade and total them. Losses are negative amounts.
| Note | Result |
|---|---|
| Trade 1: 320 USD | $320 |
| Trade 2: -140 USD | -$140 |
| Trade 3: 210 USD | $210 |
| total | $390 |
For percentage changes, such as how far a price has fallen from its high, see the percentage calculator guide. For loans and mortgages rather than investments, see the loan payment guide.
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