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Canning at altitude: adjusting time and pressure
Skipping altitude adjustments under-processes your food and can leave low-acid foods unsafe. The tables below summarize USDA/NCHFP adjustments; always apply your specific tested recipe's altitude chart.
Water boils at 212°F at sea level, but the boiling point drops about 1°F per 500 feet of elevation. Cooler boiling water means less lethality — so USDA processes compensate two different ways depending on the method.
Water-bath canning: add time
For boiling-water-bath processing, USDA increases the processing time as altitude rises:
| Altitude (ft) | Add to process time |
|---|---|
| 1,001–3,000 | +5 min |
| 3,001–6,000 | +10 min |
| 6,001–8,000 | +15 min |
| 8,001–10,000 | +20 min |
(These are the USDA increases for processes of 20 minutes or less; some recipes specify their own altitude adjustments — follow the recipe.)
Pressure canning: raise the pressure
For pressure canning, the time stays the same but the pressure (PSI) goes up with altitude — and the table depends on whether you have a dial gauge or a weighted gauge:
| Altitude (ft) | Dial gauge | Weighted gauge |
|---|---|---|
| 0–1,000 | 11 psi | 10 psi |
| 1,001–2,000 | 11 psi | 15 psi |
| 2,001–4,000 | 12 psi | 15 psi |
| 4,001–6,000 | 13 psi | 15 psi |
| 6,001–8,000 | 14 psi | 15 psi |
(Values shown are the common USDA pressures for many low-acid foods processed at "10/11 psi" at sea level; some recipes start at a different base pressure. Always use your recipe's numbers.)
Know your elevation. Look up your exact altitude before canning — being off by a bracket can mean under-processing. Weighted-gauge canners can't be fine-tuned, so above 1,000 ft they jump straight to 15 psi.
Seal applies your altitude automatically
Set your elevation once; Seal adjusts every process time and pressure to your altitude and gauge type, with voice + haptic timer prompts for hands-busy canning. Every number cited "Per USDA / NCHFP." Pay once, no subscription, works offline.
Sources
General education, not a recipe. Always follow a current USDA-tested process for your food, equipment, and elevation.