There is no measurement for the Laver because it was made of the burnished copper mirrors that belonged to the women. The women wanted to donate to the Tabernacle and they brought the mirrors that they had used to beautify themselves with in Egypt in order that their husbands should find them attractive. The Sages teach that Moses was unsure as to whether to accept their donations and God instructed him to use as many as there were and to make the Laver from them. That is why there is no predetermined measurement as it was dependent on how many there were.
