Equal to 4.025 tons. According to the conversion law of mass units, 1000 kg equals 1 ton, 25 kg equals 25 divided by 1000 equals 0.025 ton, and 4 tons plus 0.025 ton equals 4.025 ton, so 4 tons plus 25 kg equals 4.025 ton. Ton is the mathematical unit of mass, 1 ton equals 1000000 grams equals 10000000 milligrams equals 10000000 micrograms, 1 kg equals 1000 grams.