Three-quarter: 48 × 75 inches
A three-quarter mattress is commonly 48 inches wide and 75 inches long. It can suit some antique frames, compact rooms, and RV platforms. Do not assume that every old bed uses this size: the original frame should always be measured.
Short full: check both numbers
Some RV mattress lines list short full at 48 × 74 inches. That is one inch shorter than a 48 × 75 three-quarter. Other retailers may use different labels. Compare the actual width and length shown for the selected variant.
Full: a wider footprint
A standard full is commonly described as approximately 54 × 75 inches, although a seller may list 53 inches for its actual product. That extra width means a standard full is not a drop-in replacement for a 48-inch-wide bed.
Bedding and foundations
Look for sheets made for your actual dimensions and mattress depth. Check that the foundation supports the mattress across its intended footprint and meets the mattress manufacturer’s slat spacing or support requirements. An attractive antique frame may need a separate support solution.
Research notes
Size examples and product distinctions are based on the manufacturers’ published specifications. For an exact product, use its model guide and linked sources.
