Plastic Bottle Savings Calculator

How it is calculated

Three straight multiplications: bottles = per_day × 365 × years, money = bottles × price and CO₂ = bottles × 0.083 kg. The price is per bottle in dollars and the years can be fractional (0.5 is half a year, 182.5 days). The 0.083 kg per bottle is a fixed figure built into the tool; it is not adjustable and depends on bottle size, material and how the footprint is counted.

All three inputs must be greater than zero, otherwise there is no result. The bottle count is rounded to a whole number for display, but the money and CO₂ are computed from the unrounded count. Nothing is subtracted for the cost of the reusable bottle, filter or the water you still pay for, so the money figure is gross savings, not net.

Common mistakes

• Entering a weekly bottle count in the per-day field. A person who buys 10 bottles a week should enter about 1.43 a day, not 10.
• Entering the price of a multipack as the price of one bottle. The price field is per single bottle.
• Treating the money figure as net savings. The cost of the reusable bottle, refills, filters and dishwashing is not deducted.
• Treating the CO₂ number as exact. It uses one fixed 0.083 kg per bottle for every size and material, so it is an estimate to compare habits with, not a measured footprint.
• Typing years as months. Six months is 0.5 years, not 6; entering 6 projects six full years.