Whether you are making a Roman sword for a re-enactment, a theatrical production or to merely add a reminder of history to your collection, you probably want to achieve a good level of historical accuracy. The relative lengths of the blades are difficult to discern from most artistic renderings that have come down through history, and most people don't have access to authentic historical examples. Fortunately, academic study of arms and armour has arrived at a good understanding of blade lengths through the Roman period.
Make a Roman sword of the Iron Age period in a similar fashion as the swords found in Celtic cultures, including those associated with Britain up to the reign of Queen Boudica. In pre-Roman Italy, these swords had handles resembling antennae and featured two categories of blades. Slashing swords had blades of about 65 cm (26 inches) while thrusting blades were about 35 cm (14 inches).
Model a sword of the Early Roman Republic after the contemporaneous weapons of Greece, as the two cultures shared and co-developed much of their arms technology. Blades were typically bronze but were sometimes iron, and frequently a weapon incorporated both metals. Initially, the most popular sword was the kopi, which featured a blade of about 60 cm (24 inches) constructed from bronze. Kopi blades have a forward curve similar to a falcata. The other sword of the time was that favoured by the Hoplites. A Hoplite sword was the same length as a kopi although it had a straight blade that bulges near the tip.
Learn to distinguish the different styles and uses of swords from the Imperial period. The primary swords of this time were the gladius hispaniensis (usually called a "gladius"), which was popular from the time of Alexander the Great, and its replacement, the spatha, which became prominent around 100 CE. The gladius is believed to have been carried on the right leg and had a leaf-shaped blade that was typically 49.5 to 55 cm (19.5 to 21.5 inches). The spatha was the precursor to the medieval sword used by cavalry and had a generally straight blade of 65 to 70 cm (26 to 28 inches), though one discovered example had a 80cm (32 inch) blade. With its relatively uniform shape, the spatha had a blade width of about 3.7 cm (1.5 inches) before the taper.
Make a sidearm by creating a dagger similar in appearance to the gladius. The pugio had a blade of about 25 cm (10 inches) and was used throughout most of the Roman Age.
Historians speculate that Roman swords generally weighed about 900 grams (2 lb), including the hilt, handle and pommel.