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Water-bath canning recipes are tested at sea level, but lower atmospheric pressure at higher altitudes means water boils at a lower temperature — so recipes need extra processing time to safely process the same way. This calculator applies the standard USDA/National Center for Home Food Preservation altitude adjustment bands to your recipe's base processing time.
This adjustment applies to boiling-water-bath canning (jams, pickles, tomatoes). Pressure canning uses a different adjustment (to PSI, not time) and isn't covered by this calculator.
How it works
Enter your recipe's base processing time and your altitude in feet above sea level. The calculator applies the standard altitude adjustment band and returns the adjusted processing time you should actually use.
- Enter base processing time from recipe (min).
- Enter altitude (ft above sea level).
- Click Calculate to see your results.
Examples
Canning at moderate altitude
A recipe with a 10-minute base processing time at 4,500 ft altitude needs an additional 10 minutes, for a 20-minute adjusted processing time.
Canning at sea level
At or below 1,000 ft, no adjustment is needed — the recipe's base processing time applies as written.
Who should use it
- Adjusting a canning recipe's processing time for a home at altitude.
- Checking whether an altitude adjustment is needed at all for a given elevation.
Industry applications
- Home food preservation and canning
- Small-batch food production at altitude
Advantages
- Applies standard, published USDA altitude adjustment bands.
- Quick lookup before starting a canning batch.
- No account, subscription or watermark.
Limitations
- Covers water-bath canning only, not pressure canning.
- Not a substitute for a tested, safe base recipe — this only adjusts for altitude.
Common mistakes to avoid
- Using a recipe's base processing time without adjusting for altitude.
- Applying water-bath adjustments to a pressure-canning recipe, which needs a PSI adjustment instead.
Best practices
- Always know your altitude before canning and adjust processing time accordingly.
- Follow a tested recipe's base processing time exactly before applying the altitude adjustment.
Tips
- Use your specific altitude, not just your city's average, since it can vary within a region.
- Start from a tested, safe recipe — this calculator only adjusts time, not the underlying recipe safety.