Canning Altitude Pressure Adjustment Calculator
Calculate pressure canner PSI and processing time for your altitude.
Returns USDA adjustments for 1,000 to 8,000 ft for safe low-acid food canning.
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.