Enter Measurements
Example Data Table
| Shape | Diameter | Height | Length | Width | Oval diameters | Rec. width | Rec. length | Use case |
|---|---|---|---|---|---|---|---|---|
| Round | 12.0 in | 18.0 in | — | — | — | 20.9 in | 29.0 in | Fits small kitchen can |
| Rect | — | 16.0 in | 12.0 in | 10.0 in | — | 23.0 in | 29.0 in | Common compost bin liner |
| Oval | — | 17.0 in | — | — | 13.0 in / 9.0 in | 23.2 in | 30.5 in | Outdoor garden waste can |
Formula Used
This calculator sizes a liner using opening perimeter and can height. It estimates the liner as a flat rectangle that opens into a tube.
- Round opening: perimeter
P = pi x D - Rectangular opening: perimeter
P = 2 x (L + W) - Oval opening: ellipse perimeter (Ramanujan) using semi-axes
aandb - Recommended flat width:
W = (P / 2) + A - Recommended length:
Len = H + (S / 2) + O + B
A is side allowance, O is top overhang,
B is bottom tuck, and S is the top span (diameter or the longest side/diameter).
How to Use This Calculator
- Choose your units and select the can shape.
- Measure the can height and opening dimensions.
- Set overhang for the rim and bottom tuck for slack.
- Use "Recommend" for suggested liner size.
- Use "Check" to validate an existing liner.
- After results appear, download CSV or PDF if needed.
Why correct liner sizing matters for garden waste
Garden bins often handle damp clippings, soil, and prunings that add weight and create odor. A liner that is undersized can slide down, tear at the rim, or split at the base when lifted. Using the opening perimeter and height gives a repeatable sizing method instead of guessing by “gallon” labels alone. For typical household garden cans, a small width increase can reduce rim stress and prevent messy spills.
How the calculator converts shape into usable bag width
The calculator first estimates the opening perimeter. Round cans use pi × diameter, rectangular cans use 2 × (length + width), and oval cans use a Ramanujan ellipse approximation for reliable results. Flat bag width is then computed from half of that perimeter plus a user-set side allowance. This matches how liners are sold: the “flat width” is measured when the bag is laid flat, not when opened.
Length sizing: height, rim overhang, and bottom tuck
Length is built from three practical needs: coverage of the full can height, enough material to wrap over the rim, and slack to gather at the bottom. The model adds half of the top span to help the liner conform to the bottom shape, then adds overhang and bottom tuck for handling. Increasing overhang supports tie-off methods; increasing bottom tuck helps reduce “corner pull” on rectangular bins.
Interpreting the volume estimate for purchasing decisions
The volume output is a geometry-based estimate shown in liters and gallons. It helps compare your can to common liner categories, but liner fit still depends on width and length. Two cans can share a similar gallon rating yet need different flat widths because their openings differ. Use the volume as a secondary check and prioritize the recommended dimensions for reliable daily use.
Recommended setup values for common garden scenarios
For dry leaves and light clippings, start with 1 unit side allowance, 3 units overhang, and 2 units bottom tuck. For wet grass, add 0.5 to 1 unit to bottom tuck to reduce base strain. For sharp branches, increase side allowance and consider thicker liners. If you store the bin outdoors, extra overhang improves rim grip and reduces wind lift.
FAQs
1) What is “flat width” on a liner box?
Flat width is the bag’s width when laid flat and folded, measured edge to edge. When opened, the circumference is roughly twice the flat width, before allowances and stretch.
2) Why add side allowance?
Allowance compensates for seams, manufacturing tolerances, and easy drop-in. It also reduces rim tension, which lowers the risk of tears when the bin is full or damp.
3) Can I use the calculator for rectangular compost bins?
Yes. Choose the rectangular shape and enter the top opening length and width. The calculator uses the full perimeter and the longest side to estimate a stable length.
4) My liner fits width but not length. What should I change?
Increase liner length first, then adjust overhang or bottom tuck if needed. Length shortages cause slip-down and base strain. Width shortages usually prevent proper drape.
5) Does the oval option work for tapered cans?
It sizes from the opening you measure. For strong tapers, measure the top opening and consider adding extra allowance. More tuck helps the liner settle without pulling tight.
6) When should I use “Check existing liner”?
Use it when you already have a liner size on hand. Enter its flat width and length to see whether each dimension meets the recommended minimum for your can.