1. **Determine Trash Can Size**: Measure the height, width, and depth of your trash can. For round cans, measure the diameter and height.
2. **Calculate Liner Size**:
   - **Circumference**: For rectangular cans, add the width and depth, then multiply by two. For round cans, multiply the diameter by 3.14 (π).
   - **Height**: Add 3-4 inches to the height of the can to allow for overhang and tying.
3. **Select Liner Capacity**: Match the liner's gallon capacity to the trash can's volume. Common sizes include 4, 8, 13, 30, and 55 gallons.
4. **Consider Thickness**: Choose thickness based on waste type. Light waste needs thinner liners (0.35-0.7 mil), while heavy or sharp waste requires thicker liners (1.0-2.0 mil).
5. **Material Type**: Decide between high-density (HDPE) for lightweight, non-sharp waste, or low-density (LDPE) for heavy, sharp, or irregular waste.
6. **Special Features**: Consider features like drawstrings, odor control, or biodegradable options based on your needs.
7. **Test Fit**: Place the liner in the can to ensure it fits well, with enough overhang to secure it without tearing.
8. **Adjust as Needed**: If the liner is too small or large, adjust the size accordingly for optimal fit and functionality.