Door Size Finder

How to use the door size finder

1. Pick the door: a room door, a closet bifold, a front door or a sliding patio door.
2. Say what you measured. Replacing a door? Measure the old door itself, edge to edge and top to bottom (for a bifold or a slider, the opening it fills). Framing a new wall or opening one up? Measure the rough opening: stud to stud, and the floor to the header.
3. Read the door to order, its call-out (a 2′8″ × 6′8″ door is ordered as a “2868”), the rough opening it needs, and the room it leaves to walk through. Copy link keeps the result.

The rules behind the sizes

Doors are named by their size, in feet and inches

A door’s name is its width × height: a 2′8″ × 6′8″ door is 32″ × 80″, ordered as a 2868. Masonite, one of the big door makers, lists room (“passage”) doors from 12 to 36″ wide and 80, 84 and 96″ tall. The standard height is 80″; 96″ (8′) is the tall one.

The rough opening: the door + 2″ and + 2½″

A prehung door comes in its own frame, so the hole in the framing is bigger than the door. Door-frame maker Trimtek’s rule: rough opening width = the door’s width + 2″; height = the door’s height + 2½″, and for a pair of doors, both doors + 2″. JELD-WEN’s install sheet has the frame ½″ smaller than the rough opening each way: that is the room for shims.

Front doors come with their sill

An entry door is a unit: door, frame and sill. Therma-Tru’s fiberglass 36″ × 80″ unit measures 37⅝″ × 82″ and needs a 38½″ × 82½″ rough opening; its 32″ unit 34½″ × 82½″ and its 42″ unit 44½″ × 82½″.

The code wants 32″ clear to get out

The International Residential Code (R311.2) wants one door out of the house to be hinged, with 32″ clear from the open door’s face to the stop, and 78″ of headroom. The door and its stop take about 2″, which is why the NKBA writes a 32″ clear opening as a 2′10″ (34″) door. A 36″ front door leaves about 34″.

Sliders and bifolds are named by the opening

A sliding patio door fills the opening its name gives: Pella’s 6′0″ × 6′8″ slider takes a 72″ × 80″ rough opening, its frame ½″ smaller each way. A bifold closes an opening of its size; Masonite’s 48, 60 and 72″ bifolds are two 24, 30 or 36″ bifolds meeting in the middle.

Room door sizes and rough openings

An 8′ (96″) door takes a 98½″ tall rough opening. A pair of room doors, such as two 30″ doors (a 5′0″ pair), needs both widths + 2″: 62″ × 82½″.

Front door and patio door sizes

Hinged patio and French door pairs follow the same idea: Therma-Tru’s 5′0″, 5′4″ and 6′0″ units take 60″, 63″ and 72″ × 80″ rough openings.

Three worked examples

A framed opening 34″ wide and 82″ tall. A 32″ door needs 34″ × 82½″, so the width is exact and the height is ½″ short: order a 32″ × 80″ prehung door and cut ½″ off its bottom.

Replacing a 32″ × 80″ front door. The same size needs a 34½″ × 82½″ rough opening, and leaves about 30″ clear, under the code’s 32″ for the main way out. If it is the only door out, frame the opening up to 38½″ and fit a 36″ door.

A patio opening 73″ × 81″. The 6′0″ × 6′8″ slider fits its 72″ × 80″ opening with ½″ to spare on each side for shims.

Common door sizing mistakes

• Measuring the frame instead of the door. The frame and trim add 2″ or more. Measure the door slab edge to edge.
• Framing to the door’s size. A 32″ prehung door does not fit a 32″ hole: it needs 34″ × 82½″.
• A front door under 36″. A 32″ door leaves about 30″ clear: tight for furniture, and under the code’s 32″ for the main way out.
• Forgetting the floor. New tile or wood raises the floor, and the door must clear it. Measure the height from the finished floor.
• Measuring once. Measure the width at the top, middle and bottom, and use the smallest.

Read next

• Main entrance door designs
• Double door entryways
• French doors to the patio
• Space-saving doors
• Curtains over a sliding glass door