The best Renko brick size is roughly 1/20th of the instrument's current price as a fixed setting, or use the 14-period ATR if you want it to adapt to volatility automatically.
A common approach is to select a brick size that is about 1/20th of the current value of the instrument.
The ATR approach uses values generated by the Average True Range indicator, which filters out normal noise or volatility and automatically determines a good brick size.
Smaller bricks suit scalping and catch early reversals; larger bricks filter noise for swing and position trades. Test on your specific instrument before committing.