Canning Altitude Pressure Adjustment Calculator
Calculate the correct pressure canner PSI and processing time adjustments for your altitude above sea level.
Why altitude matters in canning
Water boils at lower temperatures at higher altitudes because atmospheric pressure decreases with elevation. At sea level, water boils at 100°C (212°F). At 1,800 m (6,000 ft), it boils at only 94°C (201°F). Since canning relies on reaching specific temperatures to kill botulism spores (Clostridium botulinum), you must compensate for altitude.
Boiling point at altitude:
Boiling point (°C) ≈ 100 - (Altitude in meters × 0.0034)
Boiling point (°F) ≈ 212 - (Altitude in feet × 0.00184)
Pressure canning adjustments (USDA guidelines):
For pressure canners, increase the pressure to maintain the required 116°C (240°F) internal temperature:
| Altitude | Dial Gauge PSI | Weighted Gauge PSI |
|---|---|---|
| 0–300 m (0–1,000 ft) | 11 PSI | 10 PSI |
| 301–600 m (1,001–2,000 ft) | 11 PSI | 15 PSI |
| 601–1,200 m (2,001–4,000 ft) | 12 PSI | 15 PSI |
| 1,201–1,800 m (4,001–6,000 ft) | 13 PSI | 15 PSI |
| 1,801–2,400 m (6,001–8,000 ft) | 14 PSI | 15 PSI |
| 2,401–3,000 m (8,001–10,000 ft) | 15 PSI | 15 PSI |
Note: Weighted gauge canners only have 10 and 15 PSI settings. If you are above 300 m (1,000 ft), always use 15 PSI with a weighted gauge.
Water bath canning adjustments:
For acidic foods processed in a boiling water bath, increase processing time instead of pressure:
| Altitude | Time Adjustment |
|---|---|
| 0–300 m (0–1,000 ft) | No change |
| 301–900 m (1,001–3,000 ft) | +5 minutes |
| 901–1,800 m (3,001–6,000 ft) | +10 minutes |
| 1,801–2,400 m (6,001–8,000 ft) | +15 minutes |
| 2,401–3,000 m (8,001–10,000 ft) | +20 minutes |
Worked example — green beans at 1,500 m (4,920 ft):
Green beans are low-acid and require pressure canning. The sea-level recipe says 10 PSI for 25 minutes (quart jars).
At 1,500 m with a dial gauge: increase to 13 PSI, keep the same 25-minute processing time. With a weighted gauge: use 15 PSI, keep 25 minutes.
Why this matters for safety:
Botulism toxin is destroyed at 85°C, but botulism spores survive boiling and can only be killed at 116°C (240°F) sustained for the full processing time. Underpressure at altitude means the internal temperature never reaches 116°C, leaving spores alive. This is the most dangerous food safety mistake in home canning. Always adjust for altitude.
Finding your altitude: Check your city’s elevation on a topographic map or use a GPS/smartphone altitude reading. When in doubt, round up to the next altitude bracket for safety.