A method for accurately determining a density of a fuel, the method comprising: obtaining dielectric constant versus density characteristics of the fuel at a first location; measuring a dielectric constant of the fuel at a second location, wherein environmental conditions at the second location differ from environmental conditions at the first location; and inferring the density of the fuel at the second location using the dielectric constant of the fuel at the second location and the dielectric constant versus density characteristics of the fuel at the first location; characterised in that the dielectric constant versus density characteristics of the fuel at the first location are obtained in accordance substantially with the following expression: D = K − 1 A K − 1 + B where D is the density of the fuel, K is the dielectric constant of the fuel, and A and B are constants based on the type of fuel; and in that obtaining the dielectric constant versus density characteristics of the fuel at the first location comprises: measuring a density of the fuel at the first location; using the density measured at the first location as D in the expression; measuring a dielectric constant of the fuel at the first location; using the dielectric constant measured at the first location as K in the expression; establishing a regression line for a plot of dielectric constant versus density based on the measured values of density and dielectric constant at the first location; and selecting values of constants A and B as a function of the regression line. obtaining dielectric constant versus density characteristics of the fuel at a first location; measuring a dielectric constant of the fuel at a second location, wherein environmental conditions at the second location differ from environmental conditions at the first location; and inferring the density of the fuel at the second location using the dielectric constant of the fuel at the second location and the dielectric constant versus density characteristics of the fuel at the first location; characterised in that the dielectric constant versus density characteristics of the fuel at the first location are obtained in accordance substantially with the following expression: D = K − 1 A K − 1 + B where D is the density of the fuel, K is the dielectric constant of the fuel, and A and B are constants based on the type of fuel; and in that obtaining the dielectric constant versus density characteristics of the fuel at the first location comprises: measuring a density of the fuel at the first location; using the density measured at the first location as D in the expression; measuring a dielectric constant of the fuel at the first location; using the dielectric constant measured at the first location as K in the expression; establishing a regression line for a plot of dielectric constant versus density based on the measured values of density and dielectric constant at the first location; and selecting values of constants A and B as a function of the regression line. measuring a density of the fuel at the first location; using the density measured at the first location as D in the expression; measuring a dielectric constant of the fuel at the first location; using the dielectric constant measured at the first location as K in the expression; establishing a regression line for a plot of dielectric constant versus density based on the measured values of density and dielectric constant at the first location; and selecting values of constants A and B as a function of the regression line.