Calculateur d'Ajustement de Mise en Conserve en Altitude — Formule
## How to Adjust Canning Time for Altitude
### Rule
For water-bath canning above 1,000 feet:
- **Processing time 20 min or less**: Add 1 minute per 1,000 ft above 1,000 ft
- **Processing time over 20 min**: Add 2 minutes per 1,000 ft above 1,000 ft
Water boils at a lower temperature at higher elevations (roughly 1.84°F less per 1,000 ft). The longer processing compensates for the reduced heat transfer.
### Important
This applies to water-bath canning only. For pressure canning, increase the pressure (not the time) at altitude. Always follow USDA-tested recipes.
### Rule
For water-bath canning above 1,000 feet:
- **Processing time 20 min or less**: Add 1 minute per 1,000 ft above 1,000 ft
- **Processing time over 20 min**: Add 2 minutes per 1,000 ft above 1,000 ft
Water boils at a lower temperature at higher elevations (roughly 1.84°F less per 1,000 ft). The longer processing compensates for the reduced heat transfer.
### Important
This applies to water-bath canning only. For pressure canning, increase the pressure (not the time) at altitude. Always follow USDA-tested recipes.
Exemple Résolu
A jam recipe calling for 10 minutes processing at 3,000 feet altitude.
- Base time = 10 min (under 20, so add 1 min per 1,000 ft above 1,000)
- Extra = ceil((3000 - 1000) / 1000) x 1 = 2 minutes
- Adjusted time = 10 + 2 = 12 minutes
- Boiling point at 3,000 ft = 212 - 5.5 = 206.5°F