Position Size Calculator
Calculate the ideal position size based on your risk tolerance.
- Account balance & risk %
- Entry & stop-loss price
- Shares and dollar exposure
100% free · No signup required
Smarter trades start with sharper numbers.
Most blown accounts fail at the math, not the analysis. SmartTrader gives you the four calculations professionals run before every position — instant, accurate, and free. Nothing you type ever leaves your browser.
100% free
Accurate results
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No signup
Featured calculators
Four tools, one habit: run the numbers before the trade. Jump straight to the one you need.
Risk / Reward Calculator
Check whether a setup pays enough for the risk before you take it.
- Entry price
- Stop-loss level
- Take-profit target
Compound Interest
See how your investments can grow over time — with a chart to prove it.
- Initial investment
- Monthly contribution
- Interest rate & years
Dollar-Cost Averaging
Project what steady, automatic investing adds up to over the years.
- Amount per period
- Weekly, bi-weekly or monthly
- Expected return & years
Fast & accurate
Instant results you can trust and verify against your own spreadsheet.
Built for traders
Designed around the exact questions asked before every real position.
Privacy first
Your data stays on your device. Always. There's no server to send it to.
Always free
All tools are 100% free forever. No hidden costs, no premium tier.
The trader's toolkit
Every calculation runs locally in your browser the moment you press Calculate. Nothing is uploaded or logged — your inputs are saved only on your device, so you can pick up where you left off.
Your position
Enter your account, risk and price levels, then press Calculate.
Dollar risk
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Maximum position size
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Number of shares
Trade quality
Enter your entry, stop and target, then press Calculate.
Risk per share
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Reward per share
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Risk / reward ratio
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Projection
Enter your numbers and press Calculate to see the growth curve.
Future value
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Total contributions
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Interest earned
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Balance
Contributions
Your plan
Enter your contribution plan and press Calculate.
Total invested
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Portfolio value
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Estimated gain
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Built the way a trading desk would build it
Small details compound — in your portfolio and in your tools.
Private by design
Every calculation runs in your browser. Your account size, positions and plans are never transmitted, logged or stored on any server.
Instant results
No spinners, no submissions, no reloads. Press Calculate and see sized positions, ratios and projections the same moment.
Formulas you can audit
We document exactly how each number is derived — monthly compounding, ordinary annuities, floor-rounded share counts. No black boxes.
Works everywhere
Fully responsive from a trading-desk monitor down to the phone in your pocket, with a dark mode that's easy on the eyes at the open.
Frequently asked questions
The questions traders ask us most, answered plainly.
How is position size calculated?
Start with your dollar risk: account balance × risk percentage. Divide that by the distance between entry and stop-loss to get shares, then multiply shares by entry price for the total position value. Example: a $25,000 account risking 1% gives $250 of risk. With a $48.50 entry and a $46.90 stop ($1.60 per share of risk), you can buy 156 shares — a $7,566 position.
What is a good risk/reward ratio?
Many traders look for at least 1:2 — the potential reward is twice what's risked. At 1:2 you break even winning only ~34% of trades before costs. The right target depends on your win rate: a strategy that wins 70% of the time can be profitable at 1:1, while a 30% win-rate strategy needs 1:3 or better.
How does the compound interest calculator work?
It compounds monthly: each month the balance grows by one-twelfth of the annual rate, then your contribution is added. The chart plots the balance at the end of every year against your cumulative contributions, so the gap between the two lines is pure interest.
Is dollar-cost averaging better than lump-sum investing?
Statistically, lump-sum has beaten DCA in most historical periods, because markets rise more often than they fall. DCA's edge is behavioral: it removes the timing decision, smooths your average purchase price, and makes it far easier to keep buying through drawdowns — which is where most investors fail.
How much should I risk per trade?
There is no universal number, but most professional guidance clusters between 0.5% and 2% of account equity per trade. The reason is drawdown math: at 1% risk, ten straight losses cost roughly 10% of your account — recoverable. At 10% risk, the same streak costs over 65%, which requires nearly tripling your remaining capital just to get back to even. Position sizing exists to make losing streaks survivable.
What is SmartTrader.io?
SmartTrader.io is a free collection of browser-based calculators for traders and long-term investors: position sizing, risk/reward, compound interest and dollar-cost averaging. There are no accounts, ads or paywalls, every formula is documented on the About page, and all calculations run on your device. It is an educational tool, not financial advice — see the disclaimer.
Are the calculators really free? What's the catch?
They're free, with no account, no email capture and no usage limits. Everything you type stays in your browser — see our privacy policy. SmartTrader is an educational project; nothing here is financial advice, as our disclaimer explains.
Your next trade deserves a plan
Thirty seconds of arithmetic separates a controlled loss from a blown account. Run the numbers first.
Start calculating