Here’s what you need to know:
This article explains why your DCA bot may place an initial order size larger than expected when trading Futures. This behavior is intentional and necessary to ensure the bot complies with exchange rules on minimum lot sizes.
1. What causes order size rounding?
Exchanges such as Binance and Bybit apply strict rules to all orders, especially on Futures markets. One of these rules is the lot step, the minimum increment that order sizes must follow. If the DCA bot calculates an initial order size that doesn’t match this increment exactly, the exchange will reject the order. To avoid this error, the bot rounds the initial order size up to the next valid lot step.
2. Example with BTC on Binance Futures
Let’s take an example using BTC/USDT on Binance Futures:
Lot step: 0.001 BTC
Bot calculates order size: 0.001 BTC
If the order fails due to precision issues, the bot retries with:
→ 0.002 BTC
This ensures the order can be placed successfully, even if it’s slightly higher than expected.
Why round up instead of down?
Rounding down could lead to values below the exchange’s minimum notional or quantity filters, which would also fail. Rounding up is more reliable for keeping trades executable.
3. Does this affect my strategy?
In most cases, the difference is negligible, especially on altcoin pairs with small lot steps. However, on some pairs with larger lot steps (like BTC or ETH), the difference can appear more significant and sometimes almost doubling the initial order size.
This behavior:
Does not break your DCA logic
Ensures trades are placed without interruption
Can slightly affect position sizing, especially with tight capital constraints
Additional Note:
This rounding only affects the initial base order of a DCA trade on Futures. Spot trading and manual SmartTrades may behave differently depending on the exchange.
4. Where can I check lot step settings?
You can review official lot size requirements here:
Binance Futures Trading Rules:
https://www.binance.com/en/futures/trading-rules/perpetual
Search for your specific trading pair and check the Quantity Step Size field.
5. Summary
DCA bots round up order sizes on Futures to comply with exchange lot steps.
This avoids "order size invalid" errors and ensures orders are placed successfully.
Rounding only affects the initial base order on Futures pairs.
Behavior is normal and expected and it's part of how 3Commas ensures smooth automation across different exchanges.