Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- One reusable use replaces one disposable use. Scenario calculation using your supplied factors. Defaults are illustrative inputs, not verified regional or product-specific measurements.
Example Calculation
- Reusable bag production impact: 2000 g CO₂e
- Disposable bag impact: 20 g CO₂e/use
- Reusable care impact per use: 2 g CO₂e/use
- Uses: 200
At 2000 g upfront, 2 g/use care and 20 g/use disposable impact, parity is reached at 112 uses.
Frequently asked questions
How do I use this calculator?
Enter reusable bag production impact, disposable bag impact, reusable care impact per use, uses. The result updates automatically. Use Reset to restore the example values.
What method does it use?
reusable=production+uses × care; disposable=uses × impact; parity uses=ceil(production/(disposable−care)) if denominator positive.. One reusable use replaces one disposable use. Scenario calculation using your supplied factors. Defaults are illustrative inputs, not verified regional or product-specific measurements.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.