How we check
Storage charts and substitution charts are copied from site to site, and small numbers drift along the way. These are the rules Substitute Ratio follows so that every figure on the site matches a real, dated source.
Where the figures come from
Storage times:
- Clemson Cooperative Extension, Home & Garden Information Center — Food Storage: Refrigerator & Freezer (HGIC 3522) (revised March 31, 2020); last checked 2026-09-27.
- Pacific Northwest Extension (University of Idaho, Oregon State University, Washington State University) — Storing Food for Safety and Quality (PNW 612) (revised March 2023); last checked 2026-09-27.
Substitution ratios:
- University of Illinois Extension — Substitutions for Common Ingredients (modified December 2024); last checked 2026-09-27.
- Colorado State University Extension — Ingredient Substitutions (web page); last checked 2026-09-27.
- Mississippi State University Extension — Ingredient Substitutions and Equivalents (Publication 1690, 2024); last checked 2026-09-27.
We keep a dated copy of each chart and check every figure on the site against that copy on each build. The wording on our pages is our own; only the figures come from the charts.
Storage times
- A food is listed only when both storage charts have a line for it. We match lines by what they describe; where the two lines cover different products (for example, two different kinds of canned ham), the food is left out.
- Refrigerator and freezer times are compared separately. If the charts print the same time, you see one figure. If they print different times, each is shown and credited to the chart that printed it. We do not average them or pick one.
- The only conversions we make are exact ones: a year is treated as the same as twelve months, and a week as the same as seven days. Nothing is rounded.
- Both charts describe these times as guides to eating quality, not hard limits. Clemson notes that food kept past them loses flavor and texture; Pacific Northwest Extension calls its times useful guidelines rather than set rules.
Substitution ratios: two sources, or a visible disagreement
- A swap is shown as settled only when at least two charts give the same amounts for the same ingredients.
- When charts give different amounts, every version is shown next to the others, credited to the chart that printed it.
- A swap that only one chart lists, with nothing to check it against, is left off the site until a second chart confirms it.
Gram weights
Gram columns convert cups and spoons to weight using the household portions in USDA FoodData Central (SR Legacy). When USDA lists the same unit, we use it directly; otherwise we convert from the cup weight at 1 cup = 16 tablespoons = 48 teaspoons. They are estimates: how you scoop flour or pack sugar changes the weight. When a chart does not say which kind of an ingredient to use (for example, just “vinegar” or “dry milk”), we leave the gram cell blank rather than guess.
What we do not do
No health, diet, or allergy advice — a swap here is about how a recipe turns out, not about nutrition. No product recommendations and no sponsored placements. If you find a figure that does not match its source, write to hello@substituteratio.com and we will recheck it against the original.