The best Renko brick size is 1/20th of the instrument's current price for a fixed setting, or the 14-period ATR for one that adapts to volatility automatically. Smaller bricks suit scalping. Larger bricks suit swing trading.
The 1/20th rule
The 1/20th rule sets brick size at 5% of the instrument's current price. On a $100 stock, that's a $5 brick. On a $20 stock, $1. It's a fixed setting that works as a starting point across most instruments, but because it doesn't adjust to volatility, you'll need to revisit it when conditions change.
The ATR method
The ATR method uses the 14-period Average True Range to set brick size based on recent volatility. The chart filters out normal noise automatically, so the bricks stay meaningful whether the instrument is quiet or moving. Traders prefer this approach because it adapts without manual tuning.
Smaller bricks vs larger bricks
Smaller bricks catch reversals earlier and suit scalping or short-term intraday trading, but they produce more false signals in choppy conditions. Larger bricks filter out the noise and suit swing or position trading, at the cost of slower entries. The right size depends on your timeframe and instrument.