As an Amazon Associate I earn from qualifying purchases. Links marked “Affiliate link” may earn us a commission at no extra cost to you. Learn more.
Quick answer
Amerisleep’s chart gives a queen as 60 by 80 inches and a king as 76 by 80. In the listings we read, steel frames are typically 0.5 inch smaller than the mattress in each direction (79.5 by 59.5 for a queen), wooden platform frames are 1 to 1.5 inches larger and frames with headboards and posts are 3.5 to 9 inches wider. A gap or a rim of up to a few inches is a design choice; a mattress that slides is not, and the usual fixes are mattress stoppers, a filler or a different frame.
Quick compare: the products in this guide
Sizes come from the Amazon listings as we read them; check the product page for the current details before you buy.
| Product | Listed details | Link |
|---|---|---|
| Zinus 14 Inch Rumi Metal Bed Frame, No Box Spring Needed, Black, Queen | 79.5 x 59.5 x 14 in; 27.6 lb | See details on Amazon Affiliate link |
| FinerFurnis Modern Minimalist Sturdy Wood Queen Platform Bed Frame | 81.1 x 61.42 x 7.68 in; 60.4 lb | See details on Amazon Affiliate link |
| Modway Zane King Size Spindle Bed in Walnut – Solid Wood Platform Bed Frame… | 80 x 85 x 45 in; 95 lb | See details on Amazon Affiliate link |
Real margins from listings
This is our own arithmetic, from the table values in the listings; the mattress is the Amerisleep size.
| Frame | Size | Mattress | Width margin | Length margin |
|---|---|---|---|---|
| Zinus Rumi queen | 79.5 × 59.5 in | 60 × 80 | −0.5 | −0.5 |
| Superay 18 inch queen | 79.5 × 59.5 in | 60 × 80 | −0.5 | −0.5 |
| FinerFurnis queen floor bed | 81.1 × 61.42 in | 60 × 80 | +1.42 | +1.1 |
| Modway Bridgette queen with headboard | 84 × 63.5 in | 60 × 80 | +3.5 | +4 |
| RUNSUNSPRI queen tatami base | 78 × 58 in | 60 × 80 | −2 | −2 |
| Zinus Rumi king | 79.5 × 75.4 in | 76 × 80 | −0.6 | −0.5 |
| Kartivo king with 2 drawers | 82.6 × 78.5 in | 76 × 80 | +2.5 | +2.6 |
| Modway Zane king | 80 × 85 in | 76 × 80 | +9 | 0 |
A negative margin means the frame is smaller than the mattress, so the mattress overhangs; a positive margin means a rim of bare frame around it. A steel frame 0.5 inch smaller is deliberate: the mattress stoppers sit at the edge. A wooden frame 1.42 inches wider leaves a rim of 0.71 inch on each side if the mattress is centered. A frame with a headboard is wider because of the posts and rails, and the 9 inch margin on the Zane is mostly headboard posts.
Why the numbers differ
Rails and stoppers. A steel frame’s outer size is the rails; the mattress rests on slats between them and a stopper holds it in. The mattress usually overhangs slightly.
Headboards and posts. The listed width includes them.
Mattress variation. Mattress makers vary by about an inch; the Ashley queen we read is 79.5 by 60.
Listing errors. The Avenco mattress lists a width of 39 inches, which would not be a queen.
Worked example: a gap that is too big
Suppose your frame’s inside width is 62 inches and your queen mattress is 60. The mattress has 1 inch on each side, centered, and it can slide 2 inches before it hits a rail. Two sleepers shifting weight can move it. A foam filler strip along one side, or stoppers, takes up the gap. If the inside width is 64 inches, the gap is 2 inches on each side and 4 in total, which is wide enough that a stopper alone will not hold; consider a frame that fits.
Overhang. If the mattress is 2 inches bigger than the frame, as in the tatami base, it overhangs by 1 inch on each side; that is fine on a floor base and can look uneven on a raised frame.
What to do about a gap
Measure first. Mattress and the inside of the frame, not the outer size.
Use mattress stoppers or baffles. Many steel frames include them; the Superay listing says four.
Center the mattress. Push it to the head and one side, and keep it there with a stopper.
Add a filler. A thin foam strip can fill a small gap; do not leave a gap a child could fall into.
Change the frame. If the gap is more than a couple of inches, the frame is the wrong size.
How to measure properly
Take two measurements from the frame and two from the mattress. For the frame, measure the inside width between the rails and the inside length between the headboard and footboard. For the mattress, measure the width and length with the mattress flat on the floor, not squeezed by a cover or a topper. Subtract the mattress from the inside frame measurement. A positive number is a gap; a negative number means the mattress is bigger than the space, and may not fit between the rails.
What the numbers mean
A gap of up to about half an inch is typical for a bed frame that is made to hold a mattress. A gap of one to two inches lets a mattress slide and is worth a stopper. A gap of more than two inches on a side is a mismatch. A negative gap of a few inches means the mattress is the wrong size, or the frame is for a different mattress, such as a cal king frame under a king mattress. We did not find a published standard for the acceptable gap, so these are our own rules of thumb.
Headboards and the wall
A frame with a headboard is wider than the mattress by the width of the posts, and the posts do not change where the mattress sits. If you plan to add a wall-mounted headboard to a steel frame, the frame’s width is the mattress width less half an inch, and the headboard should match the mattress, not the frame; see headboards for queen beds.
When to return the frame
If the frame is listed as one size and arrives as another, return it. In our reading, we found a “full” listing with a twin-width table row, a twin listing whose bullets said queen and a queen mattress listed at 39 inches wide, so mismatches are not rare. Check the size on the page, in the table and in the bullets, and keep a screenshot of the listing.
Mistakes to avoid
Comparing outer size with the mattress. The inside is what matters.
Ignoring the headboard. It adds width.
Leaving a gap near a child. Gaps are the hazard in our bed rails for queen size bed guide.
Buying by the name. “Queen” frames range from 58 to 63.5 inches wide in our table.
Frames by type
Steel frames with stoppers are made to be a little smaller than the mattress. Wooden platforms and floor beds are made a little larger so the mattress drops into a rim. Frames with headboards and footboards are wider and longer because the posts are included. Tatami and floor bases may be smaller than the mattress, since the mattress rests on top. Knowing which type you have tells you what to expect, and a margin that fits the type is normal.
When another guide helps
For queen frames, see queensize bed. For king frames, see king platform bedframe. For mattress sizes, see types of bed size.
A practical test is the paper test. Slide a sheet of paper into the gap between the mattress and the rail on each side; if it slides in easily and there is room for a finger, the gap is more than the half inch we call typical. Walk around the bed pressing the mattress toward each rail, and see how far it moves. A mattress that moves more than an inch or two needs a stopper or a different frame.
If you buy a new mattress, measure it before you buy the frame, not after, since mattress makers vary by about an inch and the frame’s table is the thing you can compare. Keep both measurements with the order, so that a return is straightforward if they do not match.
Frequently asked questions
Is it normal for a mattress to overhang the frame?
By about half an inch, yes, for steel frames listed at 59.5 by 79.5 inches under a 60 by 80 inch mattress.
Why is my frame bigger than the mattress?
Posts, rails and headboards add width, and wooden platforms are often 1 to 1.5 inches larger.
How big a gap is too big?
We have no standard. A gap of a couple of inches lets a mattress slide and can be a hazard for a child.
How do I stop a mattress sliding?
Mattress stoppers, or a filler strip; the Superay listing includes four stoppers.
Can a king mattress fit a cal king frame?
No. A king is 76 by 80 and a cal king 72 by 84.
Are mattress sizes exact?
They vary by about an inch between makers; the Ashley queen is 79.5 by 60.
Products worth checking
We have not tested these products. Sizes and features come from the Amazon listings as we read them; where a listing does not say, we say so.
Zinus 14 Inch Rumi Metal Bed Frame, No Box Spring Needed, Black, Queen
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
FinerFurnis Modern Minimalist Sturdy Wood Queen Platform Bed Frame
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
Modway Zane King Size Spindle Bed in Walnut – Solid Wood Platform Bed Frame with Headboard
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
Sources checked
Specifications come from the Amazon listings as we read them for this guide. Product details and availability can change, so confirm on the product page before you buy.
