Foam Toy Density and Weight Calculator
Calculate weight and firmness of EVA foam, soft polyurethane, and high-density polyurethane for toy making.
Enter dimensions and foam type for grams.
The basic math
weight (g) = volume (cm³) × density (g/cm³)
Foam toy components vary widely in weight depending on which foam you choose. The difference between soft polyurethane and high-density polyurethane is roughly 3x — same shape, three times the weight. Picking the right foam shapes both how the toy feels (firmness) and what it costs to ship.
Common toy foams and their densities
| Foam type | Density (g/cm³) | Density (kg/m³) | Pounds per cubic foot |
|---|---|---|---|
| EVA foam (craft, cosplay, bath toys) | 0.045-0.050 | 45-50 | 2.8-3.1 |
| Soft polyurethane (squeezy toys) | 0.020-0.030 | 20-30 | 1.2-1.9 |
| Medium polyurethane (cushion inserts) | 0.030-0.045 | 30-45 | 1.9-2.8 |
| High-density polyurethane (rigid components) | 0.060-0.080 | 60-80 | 3.7-5.0 |
| Polyethylene foam (closed-cell) | 0.025-0.055 | 25-55 | 1.6-3.4 |
| Memory foam (viscoelastic) | 0.040-0.080 | 40-80 | 2.5-5.0 |
| Foam rubber latex | 0.080-0.140 | 80-140 | 5.0-8.7 |
What each foam is actually used for
| Foam | Strengths | Weaknesses | Best for |
|---|---|---|---|
| EVA foam | Closed-cell, waterproof, easy cut, doesn’t compress | Stiff feel, can dent | Bath toys, cosplay armor, floor mats, foam puzzles |
| Soft polyurethane | Squeezable, compressible, soft | Open-cell (holds water), tears easily | Squishies, plush body inserts, soft squeezy toys |
| Medium polyurethane | Balance of softness and shape recovery | Open-cell | Stuffed toy structural inserts |
| HD polyurethane | Carveable, holds shape, light | Heavier than EVA | Rigid character bodies, prop weapons |
| Polyethylene (PE) foam | Excellent shock absorption, durable | Less detail-carvable | Pool noodles, protective foam |
| Memory foam | Adapts to pressure, comfortable | Slow recovery, heat-sensitive | Therapy / sensory toys |
| Latex rubber foam | Very firm bounce | Latex allergy concern | Specialty toys; avoid for children’s |
Volume calculations
For regular shapes:
- Rectangular block: L × W × H
- Cylinder: π × r² × H
- Sphere: (4/3) × π × r³
- Half-sphere: (2/3) × π × r³
- Cone: (1/3) × π × r² × H
For irregular shapes (which most toys are), use water displacement:
- Fill a graduated container with water; note the level
- Fully submerge the foam (weight it down if it floats — most foams do)
- Note the new water level
- The difference in mL equals the foam’s volume in cm³
For closed-cell EVA, weighting down is critical (it floats hard). For open-cell polyurethane, you may need to compress and release a few times to let trapped air escape.
Worked example — EVA foam sword
A foam toy sword roughly modeled as: 60 cm long × 5 cm wide × 1.5 cm thick blade, plus a 12 cm × 6 cm × 5 cm handle.
- Blade volume: 60 × 5 × 1.5 = 450 cm³
- Handle volume: 12 × 6 × 5 = 360 cm³
- Total: 810 cm³
In EVA foam (0.047 g/cm³): 810 × 0.047 = 38 g (1.3 oz) In HD polyurethane (0.064 g/cm³): 810 × 0.064 = 52 g (1.8 oz) In soft polyurethane (0.025 g/cm³): 810 × 0.025 = 20 g (0.7 oz)
The same sword weighs 2.5x more in HD poly than soft poly. For a kids’ play sword, EVA is the right choice (light but firm); HD poly is too heavy; soft poly is too floppy.
The formamide concern (EVA foam specifically)
EVA foam — especially the cheap floor-puzzle mats sold for children — has been documented to contain formamide, a residual chemical from the manufacturing process. Formamide is a reproductive toxicant classified by the EU as Category 1B (presumed human reproductive toxicant).
Key context:
- The EU banned formamide content above 200 mg/kg in toys in 2014
- Some early EVA puzzle mats tested 5,000-30,000 mg/kg — far above the limit
- The US has no federal formamide-in-toys regulation (state-level only in California, Minnesota)
- Reputable European EVA suppliers now provide formamide test reports
- Lower-priced imported EVA (Alibaba, anonymous Amazon sellers) often has no testing documentation
For children’s foam toys, especially those that will be mouthed or used by infants:
- Buy EVA from documented suppliers with REACH compliance or specific formamide testing
- Ask for the test report if buying for commercial production
- Off-gas new foam for several weeks in ventilated area before child contact (most formamide off-gasses, though slowly)
- Avoid the cheapest EVA puzzle floor mats without provenance
Other foam safety concerns
- Polyurethane foam fire-retardant chemicals: many older PU foams contain TCEP, TDCPP, or PBDE flame retardants — all now restricted in many jurisdictions but present in older stock
- Latex foam allergies: about 1-3% of population has latex allergy; can be severe
- Foam fragmentation: torn or chewed foam pieces can be choking hazards for young children. Foam toys for under-3 should be inspected regularly and discarded when torn
- Microplastic shedding: open-cell foams shed microparticles over time. Not specifically harmful at normal exposure but worth knowing
Sourcing tips
| Source | What you get |
|---|---|
| TNT Cosplay Supply, EvaFoamy, FoamiUS | Verified-source EVA, multiple thicknesses |
| Foam Factory | Custom-cut polyurethane in any density |
| Foam Order | Mattress and cushion foam, sized to order |
| Joann/Michael’s craft sheets | Pre-cut craft EVA in 12 × 18 inch sheets, $2-4 each |
| Amazon’s anonymous EVA sellers | Often cheaper but unknown formamide content |
Density and firmness — a useful intuition
Higher density = firmer foam, but also heavier. For toys, the firmness sweet spot:
- 15-25 kg/m³: very squishy, easily compressed — good for very young children
- 30-50 kg/m³: medium firmness — most plush body inserts, EVA craft foam
- 50-80 kg/m³: firm but still has some give — cosplay armor, prop weapons
- 80+ kg/m³: nearly rigid — structural toy components, harder to dent
Bottom line
Calculate the volume of your foam parts and multiply by density to get weight. EVA at 0.047 g/cm³ is the workhorse for most kids’ toys (bath toys, craft, cosplay, foam puzzles). High-density polyurethane is for rigid components. Verify formamide compliance for any EVA in children’s products. The math is simple; the safety sourcing matters more.