The cosplay prop weight calculator estimates the weight of foam, plastic, or resin props from material type and dimensions — so you can check against convention weight limits before you build.
Prop Components
Estimated Prop Weight
Component Breakdown
Estimates use average material densities for mostly-solid construction. Hollow props, surface coatings, and LEDs affect actual weight. Weigh finished props with a kitchen or postal scale for accuracy.
How to Estimate Cosplay Prop Weight
Knowing your prop's estimated weight before you build helps you make smart material choices and avoid surprises at convention check-in. Most conventions enforce a 5 lbs (2.3 kg) limit for handheld props.
Add Each Major Component
Break your prop into its main structural pieces. A sword might have a blade, crossguard, and handle. A shield might be one large piece. Enter the approximate shape (box), dimensions, and material for each piece. The calculator approximates volume and multiplies by material density.
Material Densities Explained
EVA foam is extremely lightweight at roughly 0.03 g/cm³ — a large foam sword might weigh only 250g. PLA plastic (3D printed or styrene) is about 1.24 g/cm³ — around 40x heavier for the same volume. Worbla thermoplastic runs 1.0 g/cm³ and is typically used in thin layers over foam. Wood is roughly 0.6 g/cm³ and resin about 1.1 g/cm³.
Convention Weight Limits
Most conventions allow handheld props up to 5 lbs (2.3 kg). Props for masquerade competitions sometimes have different rules. Always verify your specific convention's prop policies before the event. Oversized or overweight props may require inspection or modification at the door.
Reducing Prop Weight
If your estimate is over the limit, consider switching from PLA or wood to EVA foam for large structural sections. Hollow construction dramatically reduces weight — a hollow foam form covered with Worbla for detail work is a common pro technique. Internal structure from foam pipe or cardboard tubes adds rigidity at minimal weight cost.
FAQ
Is this cosplay prop weight calculator free?
Yes, completely free. Estimate prop weight from material and dimensions with no signup required.
What is the convention weight limit for cosplay props?
Most conventions allow handheld props up to 5 lbs (2.3 kg). Some larger events have different limits — always check your specific convention's prop rules. Oversized or overweight props may require inspection, modification, or be denied entirely. Props used in masquerade competitions have separate rules.
Which cosplay prop material is lightest?
EVA foam is by far the lightest prop material at roughly 0.02-0.04 g/cm³ (vs. 1.24 g/cm³ for PLA plastic). A large EVA foam sword might weigh 200-400g, while the same sword in PLA plastic could weigh 1-2 kg. For large props or any prop requiring convention carry, EVA foam is almost always the right choice for weight.
How accurate are the weight estimates?
These estimates use standard material densities and assume the prop is mostly solid. Hollow construction (common in prop making) will be significantly lighter. Surface coatings, paint, internal structure, and LED components add weight not included in these estimates. Weigh your finished prop with a postal or kitchen scale for accuracy.
What is Worbla and how heavy is it?
Worbla is a thermoplastic sheets material popular in cosplay for forming detailed armor pieces. It's heavier than EVA foam but lighter than most plastics, at roughly 0.9-1.1 g/cm³. It's typically used in thin layers (1-3mm) over foam cores, so the foam dominates the weight of foam/Worbla hybrid constructions.
Can I take a sword or weapon prop to a convention?
Most conventions allow prop weapons that are obviously not real, made of foam or plastic, and don't have sharp edges or projectiles. Metal, sharpened, or functional weapons are almost universally prohibited. Always check the specific convention's weapons policy before building a weapon prop — policies vary widely and are enforced at entry.