Saltwater Mix Calculator

This calculator converts a target specific gravity into a salt dose using a hobbyist-standard linear approximation rather than a precise oceanographic salinity formula: Target Salinity (ppt) is estimated as (Target Specific Gravity - 1.000) x 1400, which lands close to the commonly cited 35 ppt at SG 1.025 (roughly natural seawater salinity) and scales linearly from there. That salinity is converted to grams per gallon (parts-per-thousand is treated as grams per liter, times 3.785 liters/gallon), then scaled by Brand Mix Rate Factor -- a manual fudge factor for salt brands that measure heavier or lighter than the 1.0 reference -- and finally multiplied by Desired Volume (gallons) to produce Salt Needed (grams). Salt Needed (cups) and Half-Cup Scoops divide that gram total by an approximate 272 grams/cup bulk density, which the underlying salt-mix industry acknowledges varies by brand and how tightly the salt is packed in the scoop -- treat the cup/scoop figures as a rough kitchen-measure guide, not a substitute for a gram scale when precision matters (reef tanks especially).

Recommended Mixing Time steps up with batch size (3 hours under 20 gallons, 6 hours 20-50, 12 hours above that) because larger batches take longer to fully dissolve and de-gas chlorine/chloramine byproducts even with active circulation. Mix Temperature is fixed at 78°F/25.6°C regardless of any other input -- the standard recommended temperature for dissolving marine salt mix before use, chosen to match typical reef/fish-only tank temperatures so the freshly mixed batch doesn't shock livestock on water-change day. Total Weight adds the water's weight (at freshwater density, a slight underestimate since saltwater is modestly denser) to the dissolved salt's own weight, for planning container and stand load capacity.