If you want to prolong the life of a couch, you can recover existing cushions or make complete replacement cushions for your couch. However, don't make the mistake of buying any type of couch cover or foam slab labeled as a general couch cushion replacement. Many factors impact the size of couch cushions, and proper sizing is key before moving forward on a project.
Overall Sofa Size
The first factor in the size of the cushions on a sofa is how large the sofa itself is. Even sofas that are ostensibly the same size, such as a three-person sofa, can range several inches in length. That additional length will be reflected in the size of the cushions. A standard sized three-person sofa is 86 inches long. The size of the cushions also depends on the thickness of the arms of the sofa.
Sofa and Cushion Style
Couches now come in a number of styles. Sometimes the couch has the same number of cushions on the back and on the bottom, others have different numbers of back and bottom cushions, while others have a solid back and cushions on the seat. Obviously, a couch with three back cushions and four seat cushions has different cushion dimensions than a couch the same length with only two couch cushions. This is why knowing the style of the couch is important when determining seat size.
Standard Sofa Cushion Dimensions
Standard couch cushions are square. On a normal three person couch with smaller cushions, cushions are typically 18 inches or 20 inches square. However, larger couches often have cushions that are 24 inches square or larger. The issue becomes more complicated when you consider rectangular-shaped couch cushions, those that have cutout shapes in order to fit around the arms of couches and the notably strange couch sizes and shapes many sectional sofa cushions come in. However, these sizes give you a very good approximation.
Standard Cushion Depth
Depth is a little easier to predict than the other dimensions of a sofa cushion. Most standard sofa seat depth measurements are around 4 inches to 6 inches deep. A few manufacturers might make pieces with deeper cushions for added comfort, but 4 to 6 inches is the norm.
Measuring Your Sofa Cushions
Because sofa cushion dimensions can vary so drastically from couch to couch, it is usually best to measure your existing cushions. Unfortunately, usrd cushions are rarely the same size as they were originally. That is why you should measure both the cushions (go from seam to seam to make sure you measure the full length rather than the worn down cushion size) and the space they take up on the couch to ensure you have an accurate estimate of a full cushion size.