High Density Foam Cut to Size

High density foam is the firm, hard-wearing foam that sits inside seat cushions and keeps them supportive year after year. The word "density" describes how much material is packed into each cubic metre of foam, and on a seat that matters more than almost anything else: a denser foam holds its shape, resists the sunken, flattened look that cheaper polyether develops, and keeps giving proper support long after a low density cushion has given up. It is why high density foam is the grade upholsterers reach for, and the grade we have been cutting to size for UK customers since 1983.

We make two high density seating grades in our Bilston factory. High Firm SF38 is the workhorse, the UK trade default, and by far the most popular grade of foam in the country. Severe Very Firm SF50 is the very high density step up, for thinner cushions that still need to feel firm. Both are open-cell polyurethane foams, both meet the Furniture and Furnishings (Fire) (Safety) Regulations, and both can be ordered cut to size to any shape, with a simple rectangle needing nothing more than three measurements and a shaped cushion supplied as a paper template at no extra cost.

Density and firmness are often confused, but they are not the same thing. Density is the weight of foam per cubic metre and is the best single guide to how long a cushion will last. Firmness (sometimes called hardness) is how the foam feels when you sit on it. A good seating foam needs both: enough density to survive years of daily use, and a firmness that suits the job. High density foam delivers the durability, and the grade you pick sets the firmness.

For seating, low density foams are a false economy. They feel fine in the showroom, then soften and lose height within months. High density grades like our SF38 and SF50 cost a little more by volume but outlast the cheap alternatives many times over, which is exactly why the upholstery trade specifies them as standard.

High Firm SF38. The high density quality seating grade and the UK trade default. Suitable for sofa and armchair cushions, dog and other pet beds, VW Camper foam, campervan cushions, narrowboat saloon benches, static caravan lounges, pallet furniture and much more. Designed for cushion thicknesses between 3 and 5 inches (7.5 to 12.7cm). By far the most popular grade of foam in the UK.

Severe Very Firm SF50. A very high density seating grade for foam cushions less than 3 inches (7.5cm) thick, where a thin pad still has to feel firm and supportive. Typical uses include window seat cushions, quality dining chairs, kitchen seats, office chair seat refoams, and vehicle restoration projects where a period-correct density matters.

If your project calls for something softer, our full range of foam grades includes Medium SF33 for back-rest cushions and lighter-use seats, and Reflex for premium high-resilience seating. If you are not sure which grade fits, the densities and firmnesses are compared side by side on the foam grades and types page, or you can call us and we will talk it through.

Choose High Firm SF38 for cushions 3 to 5 inches thick. This covers the great majority of domestic and leisure seating: sofa and armchair seat cushions, replacement foam cushion refills, pet beds, camper and campervan cushions, narrowboat and static caravan seating, and pallet furniture seating. If in doubt for an everyday seat, SF38 is the right answer.

Choose Severe Very Firm SF50 when the cushion is under 3 inches thick and still needs to feel firm. Thin pads have less foam to work with, so a higher density keeps them supportive rather than bottoming out. This is the grade for window seat cushions, quality dining and kitchen chairs, office chair refoams, and vehicle restoration where the original specification was a dense, firm pad.

Thickness and grade go together. As a rule of thumb, anything from 3 to 5 inches (7.5 to 12.7cm) suits High Firm SF38, while cushions thinner than 3 inches (7.5cm) are better in Severe Very Firm SF50 so they keep their support. When you order, measure the depth you want the finished cushion to be, and if you are refilling an existing cover, measure the cover rather than the old foam, which may have flattened over the years. Adding a polyfibre (Dacron) wrap softens the edge profile and helps the cushion hold its shape, and it is worth specifying where the look matters as much as the comfort.

Ordering is straightforward. For a rectangular cushion, choose the rectangle shape in the selector above, enter your width, depth and thickness, and pick your grade. For a shaped seat, choose the nearest shape or "your template", and send us a paper template so we can cut the cushion exactly to fit, at no extra cost. We cut everything in house at our Bilston factory, include stockinette to help the foam slip into your cover, and deliver free on the next working day, with VAT already included in every price.

We are the UK's largest online foam store, manufacturing in Bilston, West Midlands since 1983, and working to ISO 9001 quality standards. Every order is cut to size in our own factory, delivered free on the next working day, and priced with VAT included so the figure you see is the figure you pay. High density seating foam is our core business, and High Firm SF38 in particular is the grade we cut more of than any other, so when you order it you are buying the foam the UK trade trusts, from the people who cut it every day.

If you would rather talk it through than work it out from a spec sheet, call us free on 0800-0439990, or drop a line via the contact page and we will come back to you the same working day.

What is high density foam?
High density foam is a firm, hard-wearing open-cell polyurethane foam used for seating where support and long life matter. Higher density means more material in each cubic metre, so the foam holds its shape and resists going soft. Our two high density seating grades are High Firm SF38, the UK trade default, and Severe Very Firm SF50 for thinner, heavier-duty cushions.

What is the difference between High Firm SF38 and Severe Very Firm SF50?
High Firm SF38 suits cushions between 3 and 5 inches (7.5 to 12.7cm) thick, such as sofa and armchair seats, and is the most popular foam in the UK. Severe Very Firm SF50 is for cushions under 3 inches (7.5cm), where a thin pad still needs to feel firm, for example window seats, dining chairs and office chair refoams.

Is high density foam good for sofa cushions?
Yes. High Firm SF38 is the standard choice for sofa and armchair cushion replacements at the usual 3 to 5 inch thickness, giving firm, lasting support.

How thick should high density foam be?
High Firm SF38 is designed for cushions 3 to 5 inches (7.5 to 12.7cm) thick. For thinner cushions under 3 inches (7.5cm), Severe Very Firm SF50 keeps the seat firm and supportive.

Can high density foam be cut to size?
Yes. Order online to your exact dimensions: rectangles need only simple measurements, and shaped cushions can be supplied as a paper template at no extra cost. Everything is cut at our Bilston factory and delivered free on the next working day.

Is high density foam fire retardant?
Yes. Our upholstery grade high density foams meet the Furniture and Furnishings (Fire) (Safety) Regulations 1988 and amendments, so they are suitable for domestic seating and upholstery.