Plan garden seat cushions with confidence quickly today. Enter dimensions, choose shape, and set quantity. Get volume, foam weight, and unit conversions instantly here.
| Use case | Shape | Inputs | Quantity | What you get |
|---|---|---|---|---|
| Patio chair seat | Rectangular | 45 × 40 × 8 cm | 2 | Total volume and estimated weight |
| Round bistro cushion | Round | Diameter 35 cm, thickness 6 cm | 4 | Volume in liters and cubic feet |
| Backrest wedge | Wedge | 50 × 40 cm, T1 10 cm, T2 4 cm | 1 | Tapered volume using average thickness |
Garden benches and patio chairs rarely match off‑the‑shelf cushion sizes. Measuring the seat area and selecting a shape helps you buy foam sheets efficiently. Use rectangular for standard pads, round for bistro seats, wedge for angled backrests, and bolster for roll pillows. Consistent inputs reduce cutting waste and improve fit. Record fabric seam allowances too, because cover thickness and piping can slightly reduce interior space.
Select one unit system for the whole job, then measure twice with a tape or ruler. Small errors in thickness can change volume noticeably because thickness multiplies the full footprint. When covers are tight, subtract 2–5 mm (or 1/8 in) from length and width for easier insertion. Add 5–10% volume allowance if you expect trimming and shaping.
The calculator converts dimensions to meters internally, calculates cubic meters, and then reports liters and cubic feet for quick purchasing comparisons. Liters are useful when matching packaged foam fill, while cubic feet helps when comparing sheet sizes sold by thickness. For multiple cushions, quantity scales the total volume linearly, so you can plan one cut pattern and replicate.
Density affects carrying weight and perceived support. For outdoor seating, common densities often fall around 25–45 kg/m³, while firmer applications can go higher. The weight estimate is volume multiplied by density, so increasing thickness or choosing firmer foam increases both comfort and lift effort. Heavier cushions may need stronger ties or non‑slip bases.
After calculating, compare the total volume with sheet dimensions available locally. If a supplier sells foam by sheet area and thickness, focus on per‑piece volume and thickness to estimate how many pieces fit on one sheet. For round or bolster shapes, plan extra margin for circular cutoffs. Download the CSV for records and the PDF for sharing with vendors.
No. Measure the finished interior space of the cover when possible. If the cover is tight, reduce length and width slightly so the foam slides in without compressing seams.
For simple rectangles, 5% is often enough. For circles, wedges, and bolsters, plan 5–10% extra because curved cutoffs and alignment errors can create unusable scraps.
Many outdoor seat cushions use foam around 25–45 kg/m³. Higher densities feel firmer and last longer under load, but they also weigh more and may cost more.
Volume equals footprint area multiplied by thickness. A small thickness change affects every square unit of the cushion surface, so even a 1 cm increase can add liters of foam.
Yes. Choose the wedge option and enter the two thickness values. The calculator uses the average thickness to estimate volume for a smooth, linear taper.
Use CSV to store project records and compare multiple cushion sets. Use the PDF when sharing requirements with a supplier, upholsterer, or team member on site.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.