I know what the correct 3D printer belt tension is! Let me explain what it is and how to set it! - Lost in Tech

good is around 2.5kg to 2.8kg, (through a luggage scale) more than 3kg is a bad advice.

Belt tensioning

To actually measure the tension the easiest and most precise way is via its vibration frequency.

• On the Ender 3 specifically, with the hotend carriage against the limit switch, the belt between the carriage and idler is 0.302 meters (302mm) long, so the target frequency is 86 Hz.

• Again on the Ender 3, with the bed pushed all the way back, the exposed belt is 0.253 meters (253mm) long, so the target frequency is 112 Hz.

You can measure the frequency with the Spectroid app for Android.