Fresh batch mix
RO/DI volume + target salinity → salt mass in grams. Done.
Salt mix calculator
Reef salt mix calculator.
How many grams of salt to hit 35 ppt in 100 liters? How much to adjust a water change? Use the free ReefFlow calculator — in-app and on the web.
Stop guessing salt amounts.
Mixing salt half-asleep on Saturday morning sounds simple but hides traps. 35 or 36 grams per liter? Will that 20L bucket end up at 22L once the salt dissolves? Refractometer reads 1.024 — how much do I add to bring a 300L system up to 1.026?
The ReefFlow salt mix calculator answers those questions in seconds. Enter freshwater volume (RO/DI), target salinity, get exact salt mass. It also goes the other way: from current 1.024 to target 1.026 across 300L — what is the dose?
The calculator is free, lives inside the app and on the web at reefflow.com.br/en/calculators. Bundled with calculators for alkalinity, Ca/Mg dosing, water change volume and refractometer correction.
Who it is for
- Reefers who mix salt weekly and want exact doses
- Brand-specific users (Red Sea, Tropic Marin, Instant Ocean)
- Anyone fixing salinity in an existing system
- New tank builders calculating initial salt stock
- Nano keepers who do not want to waste salt
- Refractometer users who occasionally need correction
Existing tank adjustment
Current salinity, target salinity, system volume → how much new saltwater to add.
Other reef calculators
Alkalinity, Ca, Mg, water change, refractometer. All in the same app.
Web access too
Use it in the app or directly in the browser at reefflow.com.br/en/calculators — no install needed.
Saves history
Each calculation is saved. Remember how much salt you used last water change.
Web and mobile
Use it on phone, tablet or directly at reefflow.com.br/en/calculators.
Mix salt in seconds. Hit it on the first try.
Use it in the app (free for iOS and Android) or directly in the browser.
FAQ — salt mix calculator
How many grams of salt per liter of fresh water?
On average 35-40g per liter of RO/DI to reach 35 ppt (1.026 SG). Exact varies by brand — some require 36g/L, others 38g/L. The calculator factors in volume and target.
Does the calculator account for different salt brands?
It uses standard ratios. For brand-specific tuning, measure salinity post-mix with a refractometer.
Can I use it to adjust an existing tank?
Yes. Adjustment mode takes system volume, current salinity and target, and returns the new saltwater volume to add.
Is the calculator free?
Yes, fully. Works in the app and on the web without login.
Are there alkalinity calculators too?
Yes. Alkalinity, Ca/Mg, water change volume, refractometer, electricity cost, heater, substrate — all free.
Do I need to install anything?
No. The calculator runs in the app and on the web at reefflow.com.br/en/calculators, without login.