The average salinity of the ocean water is

The average salinity of the global ocean is approximately 35 parts per thousand (ppt or ‰) [1][t1]. Salinity is defined as the total content of dissolved salts in seawater, calculated as the amount of salt in grams dissolved in 1,000 grams of water [3]. While expressed as 35 ppt, this value is equivalent to 3.5% by weight, as 35 parts out of 1,000 equals 3.5 parts out of 100 [t2][t10]. Although specific regions vary—such as the Baltic Sea at 7 ppt or the Red Sea at 39 ppt due to evaporation and freshwater influx—the global mean remains consistently cited at 35 ppt [1][c4]. This concentration is primarily composed of sodium and chloride ions, which account for over 90% of the dissolved minerals [t2]. Therefore, 3.5% is the correct percentage representation of the average ocean salinity.

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 12: The Oceans > Salinity of the Ocean > p. 107
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 33: Ocean temperature and salinity > 33.2. Ocean Salinity > p. 518
3. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 12: Water (Oceans) > SALINITY OF OCEAN WATERS > p. 104