Calculator Inputs
Example Data Table
| Shape | Dimensions | Fill | Loft | Overstuff | Count | Estimated Weight Each | Estimated Total Weight |
|---|---|---|---|---|---|---|---|
| Square | 20 in × 20 in × 4 in | Polyester (Medium) | 1.10 | 10% | 2 | ~340 g | ~0.68 kg |
| Bolster | 24 in length, 7 in diameter | Foam Crumb | 1.05 | 5% | 1 | ~1,000 g | ~1.00 kg |
Example values are illustrative. Actual weight varies by manufacturer and packing method.
Formula Used
Step 1: Compute cushion volume
- Rectangular/Square:
V = L × W × T - Round:
V = π × (D/2)² × T - Bolster:
V = π × (D/2)² × L
Step 2: Apply practical fill adjustments
V_adjusted = V × LoftFactor × FirmnessFactor × (1 + Overstuff%/100)
Step 3: Convert adjusted volume to weight
Weight = V_adjusted(L) × Density(g/L)
How to Use This Calculator
- Select your units and cushion shape.
- Enter dimensions and seam allowance if your cover fits tight.
- Choose a fill type or enter a custom density.
- Set loft, firmness, and overstuff to match your comfort goal.
- Click Calculate to see weights above the form.
- Use the download buttons to save CSV or PDF results.
Cushion Fill Planning Article
1) Why fill weight matters outdoors
Outdoor cushions face moisture, heat, and repeated compression. Underfilled inserts feel flat, shift inside the cover, and recover slowly after sitting. Overfilled inserts strain seams, distort shapes, and can reduce breathability. Estimating fill weight from volume helps you buy the right amount once, control comfort, and avoid unnecessary material waste.
2) Volume and shape selection
This calculator converts common cushion shapes into a usable volume. Rectangular and square cushions use length, width, and thickness. Round cushions use diameter and thickness. Bolsters use diameter and length. Seam allowance expands the effective cut size, reflecting how tight covers can increase the perceived fill requirement, especially for boxed edges and piping.
3) Density, loft, and firmness data
Fill density links volume to weight and varies widely by material. Lightweight options like down blends occupy more volume per gram, while heavier media like buckwheat hulls add substantial mass. Loft factor represents fluff and spring-back. Firmness factor nudges the fill volume higher for a firmer feel. These multipliers help match real-world comfort preferences.
4) Overstuff strategy for longer life
Overstuffing is a practical allowance that counters settling over time. For lounge seating, a 5–15% overstuff range often improves edge support and reduces “pancaking.” For decorative cushions, lower overstuff can preserve shape and drape. Track your preferred settings and reuse them for consistent results across sets.
5) Purchasing and installation tips
Buy a small buffer for testing and topping up, especially when switching brands. Weigh fill as you add it to the insert, then distribute evenly before closing. If using shredded foam, break up clumps and rotate the insert during filling. After a day of expansion, reassess loft and adjust before final stitching or zipping.
FAQs
1) Why does my cushion need more fill than expected?
Tight covers, boxed edges, and firm preferences increase required fill. Also, some fills compress more during stuffing. Try a higher loft factor or 5–15% overstuff, then compare the feel after full expansion.
2) What density should I use for a custom fill?
Start by weighing a known volume. Fill a container with one liter volume, weigh the fill in grams, and use that value as g/L. This aligns the calculator with your exact material batch.
3) Should I measure the cover or the insert?
Measure the finished cover interior for best results. If you only have cut fabric sizes, include seam allowance to approximate the finished dimensions. For very tight covers, add a small seam allowance buffer.
4) How do I reduce lumps in shredded foam fills?
Break apart clumps before filling and add in small portions. Shake and rotate the insert frequently. A light mist of water can reduce static in dry climates, improving distribution during stuffing.
5) Why is buckwheat so heavy for cushions?
Buckwheat hulls have high bulk density compared to fiberfill or down. They provide firm, supportive seating, but add significant weight. Confirm that zippers, seams, and furniture frames can handle the mass.
6) What overstuff value is best for patio seating?
For seat cushions, 10–20% often improves support and slows sagging. For back cushions, 5–12% is common to keep comfort without pushing you forward. Adjust based on cover tightness.
7) Can I use this for replacement inserts?
Yes. Use your existing insert dimensions and choose a similar fill type. If the old insert has settled, increase overstuff slightly. Record your final settings to replicate consistent comfort later.