Paper or plastic — which bag is actually better?
The honest answer depends on re-use, which is exactly what most comparisons leave out.
Compared on: carrying one shop's worth of groceries, once
Single-use plastic bag (used once)
0.033 kg CO₂eLightweight HDPE, ~8 g of polymer plus conversion.
Source: Published packaging LCA ranges (HDPE carrier bags)
Paper bag (used once)
0.080 kg CO₂eHeavier material and a more energy-intensive process than thin plastic.
Source: Published packaging LCA ranges (kraft paper carriers)
Cotton tote (used once)
1.7 kg CO₂eCotton agriculture dominates; terrible if used once.
Source: Published textile LCA ranges
Cotton tote (used 100 times)
0.017 kg CO₂eSame bag, footprint spread across 100 shops — now the best option.
Source: Same LCA, amortised over re-use
What this means
- Per single use, thin plastic is lower carbon than paper — the plastic problem is waste and litter, not only carbon.
- A cotton tote only wins after roughly 50–100 uses, so the rule is simple: own few bags and use them for years.
- Bags are grams; the food inside them is kilograms. Prioritise accordingly.
Your own number, not an average
Averages answer the question; your own footprint tells you what to change first. The calculator takes about two minutes and needs no account.
Figures are averages drawn from public databases and peer-reviewed LCA work; see our methodology for how each factor is applied.