Canning Processing Time by Altitude Calculator

How it works

adjusted time = base time + altitude addition · addition depends on altitude band and whether base ≤ 20 min

Water boils at a lower temperature as altitude rises, so a boiling-water bath transfers less heat and needs more time to destroy the same spoilage organisms. The USDA/NCHFP tables add a fixed number of minutes by altitude band, and the addition is larger for recipes that already process more than 20 minutes. This adjustment is for boiling-water and atmospheric-steam canning — for a pressure canner you raise the pressure for altitude instead of extending time. Always start from a tested recipe's sea-level time; these adjustments modify a validated process, they do not replace it.

Worked example

A pickle recipe calls for a 15-minute boiling-water process at sea level. At 4,500 feet (the 3,001–6,000 ft band), a process of 20 minutes or less gets +10 minutes, so you process for 25 minutes. A 30-minute recipe at the same altitude would instead add 20 minutes, for 50 minutes total.

Sources: National Center for Home Food Preservation — Altitude adjustments

Frequently asked questions