Food Miles Calculator vs Plastic Footprint Calculator
Two Ecology-category calculators look at different slices of the same grocery bag. The food miles calculator estimates the greenhouse-gas emissions from shipping food over a single transport leg. The plastic footprint calculator annualizes the mass of the plastic items you use. Both are scenario worksheets rather than full lifecycle footprints, and both insist that you record your own measurements and factors — the genuine choice between them is which environmental slice of your shopping you want to measure.
What each calculator does
The Food Miles Calculator takes shipment mass in kilograms, distance in kilometres, and a nonnegative emissions factor in kg CO₂e per tonne-kilometre. It computes tonne-kilometres as mass ÷ 1,000 × distance, then transport emissions as tonne-kilometres × factor, without intermediate rounding. The factor is never supplied by the page: you record its transport mode, geography, year, system boundary, and version. Its worked example — 500 kg over 1,000 km at 0.062 kg CO₂e/t-km — gives 500.0 t-km and 31.0 kg CO₂e.
The Plastic Footprint Calculator takes items per week, measured grams per item, and the weeks represented. Annual mass = items/week × g/item × weeks ÷ 1,000. You define exactly what counts as one item and how its mass was measured, recording scale or method version and uncertainty. Its worked example — 20 items per week at 12 g over 52 weeks — gives 12.48 kg/year, and cutting frequency to 15 items per week saves 3.12 kg/year at the same item mass.
Side-by-side comparison
| Feature | Food Miles Calculator | Plastic Footprint Calculator |
|---|---|---|
| Question | What are the transport-only emissions of shipping this food? | What is the annual mass of the plastic items I use? |
| Inputs | Shipment mass (kg), distance (km), entered kg CO₂e/t-km factor | Items per week, measured g/item, weeks |
| Method | t-km = kg ÷ 1,000 × km; emissions = t-km × factor | Items/week × g/item × weeks ÷ 1,000 |
| Output | Tonne-kilometres and kg CO₂e, one decimal | Annual mass in kg/year, two decimals |
| Data discipline | Factor source, version, and boundary required | Item definition, measurement method, and uncertainty required |
| Coverage | One transport leg only | Entered item definition and period only |
When to use which
Use the food miles calculator when you want to quantify the transport leg of food — comparing route distances, testing factor sensitivity with documented high and low factors, or auditing a multi-leg journey one mode at a time. It excludes food production, packaging, refrigeration, retail, cooking, and waste, and it is not a product footprint, inventory, certification, or offset quantity. Keep the entered factor on the same tonne-kilometre basis as the distance you enter.
Use the plastic footprint calculator when you want to annualize the mass of a clearly defined plastic item or item group — establishing a repeatable baseline, then testing one change at a time (frequency, item mass, or weeks) while holding everything else fixed. The result excludes uncounted plastics, attached contents, secondary packaging, and all downstream collection, recycling, disposal, and emissions, so it should not be compared with regional per-capita statistics unless definitions, years, and boundaries are aligned.
Both pages share the same discipline: record your measurements and assumptions so a later run is reproducible. If you want the full lifecycle emissions of the food itself rather than just transport, the meat footprint calculator covers that; these two tools cover the shipping leg and the packaging mass, respectively.
Where to start
- Food Miles Calculator — transport-only emissions from mass, distance, and an entered factor.
- Plastic Footprint Calculator — annual mass scenario from item frequency and measured mass.