Equations for estimating milk density at 4°C from fat, protein, and lactose and other solids (LOS) contents were developed based on data collected over a whole year from Ontario and Alberta milk producers. Density was measured by an Anton Par Model DMA 45 density meter. Although milk density was mainly explained by composition, including seasonal factors in equations increased accuracy. "Weight over weight" to "weight over volume" conversions of milk components employing the developed equations were equivalent to the calculation with empirical density. The average difference between estimated and actual w/v values was 0.000 with the standard deviation of 0.002. Density of producer milk at 4, 16, 28, and 40°C was determined, and an equation for density estimation at any temperatures between 4 and 40°C was constructed. A formula with a cubic term of the temperature exhibited the best density prediction with the standard deviation of residuals of 2.31 e-4.