Canning Processing Time Calculator
Adjust a tested canning recipe's processing time for your altitude, using the correct USDA increment, plus the right gauge pressure for pressure canning.
Why processing time matters in canning:
Canning processing time is not optional or approximate — it is the scientifically tested minimum required to destroy harmful microorganisms, including Clostridium botulinum (the bacterium that causes botulism). Using shorter times or skipping steps creates a genuine health risk.
Two canning methods:
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Water Bath Canning (BWB): Used only for high-acid foods (pH ≤ 4.6). Boiling water at 212°F (100°C) is sufficient to kill mold, yeast, and most bacteria in acidic environments.
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Pressure Canning: Required for ALL low-acid foods (vegetables, meats, beans, soups). Reaches 240°F (116°C) at 10 PSI, which destroys botulinum spores that survive boiling water.
High-acid foods (water bath only):
| Food | pH | Water Bath OK? |
|---|---|---|
| Jam, jelly, marmalade | 3.0–4.0 | Yes |
| Pickles (properly acidified) | 3.5–4.4 | Yes |
| Tomatoes (with lemon juice added) | 4.0–4.6 | Yes |
| Fruit and fruit juices | 3.5–4.2 | Yes |
| Salsa (tested recipe) | 3.5–4.5 | Yes |
Low-acid foods (pressure canning only):
Vegetables, beans, corn, peas, meats, poultry, fish, soups, stews — ALL require pressure canning.
Altitude adjustment for water bath canning:
Water boils at lower temperatures at higher elevations, so processing times must increase. There are two ladders, and which one you use depends on the length of the sea-level process:
| Altitude | Process of 20 min or less | Process over 20 min |
|---|---|---|
| 0–1,000 ft | No adjustment | No adjustment |
| 1,001–3,000 ft | Add 5 minutes | Add 10 minutes |
| 3,001–6,000 ft | Add 10 minutes | Add 20 minutes |
| 6,001–8,000 ft | Add 15 minutes | Add 30 minutes |
| 8,001–10,000 ft | Add 20 minutes | Add 40 minutes |
People miss that second column constantly. A 45-minute quart of tomatoes at 5,000 ft needs 65 minutes, not 55.
Altitude adjustment for pressure canning:
Instead of increasing time, increase pressure. The time stays exactly as the recipe states.
| Altitude | Dial gauge | Weighted gauge |
|---|---|---|
| 0–1,000 ft | 11 PSI | 10 lb |
| 1,001–2,000 ft | 11 PSI | 15 lb |
| 2,001–4,000 ft | 12 PSI | 15 lb |
| 4,001–6,000 ft | 13 PSI | 15 lb |
| 6,001–8,000 ft | 14 PSI | 15 lb |
| 8,001–10,000 ft | 15 PSI | 15 lb |
The weighted gauge only has two positions, and the switch happens at 1,000 ft, not 2,000. If you live above 1,000 ft and have been using the 10 lb weight, you have been under-processing every low-acid jar.
A note on jar size: this calculator deliberately has no jar-size input. There is no formula that converts a pint time into a quart time. Heat travels to the centre of a quart jar differently, and the tested times are established by measuring it, not by arithmetic. Read the row for your jar size off the recipe. A larger jar never needs less time than a smaller one.
Standard processing times (base, sea level, pint jars):
| Food | Water Bath | Pressure Can |
|---|---|---|
| Jams and jellies | 10 min | N/A |
| Pickles (sliced) | 15 min | N/A |
| Tomatoes (crushed, acidified) | 35 min | 15 min at 10 PSI |
| Green beans | Not safe | 20 min at 10 PSI |
| Corn (whole kernel) | Not safe | 55 min at 10 PSI |
| Chicken (boneless) | Not safe | 75 min at 10 PSI |
Always use tested recipes from the USDA Complete Guide, Ball Blue Book, or the National Center for Home Food Preservation. Homemade recipes are not safe for canning — only tested recipes have verified processing times.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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