Report a fish-brine calculation clearly
For a recipe that explicitly specifies an example 4% of water weight, 750 g water requires 30 g plain salt. For 4% of salt plus water, the same water amount requires 750 × 4 ÷ 96 = 31.25 g salt.
Record the water amount, percentage and denominator alongside the result. A label such as “4% brine” alone leaves the calculation ambiguous. Neither amount above specifies a soaking duration, smoking method or safe storage condition for fish.
Start with the recipe’s definition
Fish-brining recipes can describe salt relative to water alone, the combined salt-and-water solution, or food plus water. These are different denominators. A percentage without a definition is not enough to calculate a repeatable batch.
The starting 3% value above is an arithmetic example. It is not a recommended brine strength for fish. Use the ratio specified by the tested process you are following.
Same percentage, different salt amounts
With 2 litres of water, a 5% water-based recipe requires 100 g salt. A 5% solution-based recipe requires 105.26 g salt. The latter divides salt by salt plus water, rather than water alone.
If a recipe uses food plus water, weigh both and choose that basis. For 1,000 g fish and 1,000 g water at an example 2%, the ingredient ratio gives 40 g salt, excluding added salt from the denominator.
Initial brine is different from finished fish
The percentages above describe ingredients before processing. The calculator cannot determine the salt absorbed by the fish or its finished water-phase salt. It does not calculate a brining time from fillet weight.
For smoking, curing or storage, follow a tested process covering the fish, thickness, temperature, treatment and storage conditions. Do not use the calculator's result alone to establish shelf life.
Mass, volume and measurement
Weigh salt rather than converting a spoon or cup measurement across salt brands. Water volume is approximated at 1 g/mL. If you need an exact final volume of brine, a water-volume calculation alone is insufficient.
Oregon State University's Preparation of Salt Brines for the Fishing Industry explains salt-by-weight concentration, volume changes and temperature-dependent salometer readings. Its process examples are not defaults for this calculator.