Above: Illustration of the only confirmed Macuahuitl extant until modern times - destroyed in 1884 in a fire in the Armería Real in Madrid, where it was housed beside the last tepoztopilli (a PreColumbian spear made in a similar fashion to the Macana with Obsidian Teeth).
Fortunately measurements survive:
TL: 84 cm Cutting Surface L: 57 cm Handle L: 26 cm Cutting Surface W: 4 or 5 cm Individual Inset Blade L: 2 cm
The following given in the recently updated Macuahuitl Wikipedia article (probably as general weights and lengths for Macuahuitl designated for warfare:
Weight:2.0–3.0 kg Length:90-120 cm
We also have many artistic representations still available, both Meso American and Spainish.