What is diagonal depth?

Diagonal depth is the straight line measured from the highest point of a sofa back down to the front bottom edge of its base. When a sofa is tilted onto its side and carried through a doorway, that line is the profile passing through the opening, which is why it decides the fit rather than the sofa depth.

How do I calculate diagonal depth of a sofa?

Take the back cushions off. Hold a straight edge or a taut string from the top back corner of the frame to the front bottom edge of the base, keeping it straight rather than following the upholstery, and measure that line. On most three seater sofas it comes out 4 to 8 in less than the sofa depth.

Why is diagonal depth smaller than sofa depth?

Because the sofa is not a rectangle in profile. The back leans, the base is set back from the arm face, and the widest horizontal measurement across the piece is not the same as the shortest line through it when it is turned. Tilting takes advantage of that difference.

What diagonal depth do I need for a 30 inch door?

A 30 in door gives about 28.5 in of clear opening once the stops are counted. A diagonal depth under 28 in goes through with usable margin. Between 28 and 28.5 in it will go, but take the door off its hinges first, which buys about 2 more inches.

Does diagonal depth apply to sectionals?

Yes, but measure each piece separately. A sectional is delivered and moved as individual units, so the diagonal of the largest single piece is the number that has to clear the door. The assembled footprint never passes through anything.

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Home / Doorway & Entry Clearance

Sofa Diagonal Depth Calculator

Diagonal depth is what passes through the doorway when a sofa is tilted, and it is smaller than the sofa depth.

Trusted across thousands of fit checks · updated daily

400 questions answered

Room Preview·Visual Results·Simulations

Fit summaryFIG. CLEARANCE

Whether it fits comes down to the measurements most people skip.

The tilted profile, not the sofa depth, is what has to clear the stops.

The spaceInterior door 28 to 30" clear. Bedroom door 30 to 30.5" clear. Entry door 34 to 36" clear

What decides itDiagonal depth vs. door clear opening width

What to measureStandard three seater sofa: 35 to 38" deep, diagonal depth about 26 to 30". Loveseat: 34 to 36" deep, diagonal about 25 to 28". Measure yours for an exact verdict

Real openings run about 1 to 2 inches under the labeled size, and a single inch can flip the result. Check your own measurements before you buy or move.

ReferenceDoor Guide Furniture Dimensions Door Sizes by Country

About 10 seconds · no signup

Verdicts compare all six item orientations against the space using verified building standards. See our methodology

10,000+ fit checks run·Last check: a few minutes ago

“Checked my mattress before ordering. Tight fit, but it worked with the door removed.” — Online shopper

Measure smart

What to measure.

Four numbers decide nearly every fit check. Get these right and the rest follows.

01Diagonal depth: hold a straight edge from the highest point of the sofa back down to the front bottom edge of the base, and measure that straight line. It is the profile that passes through a doorway when the sofa is tilted
02Sofa depth for comparison, measured horizontally from the back to the front edge. Expect the diagonal to come out 4 to 8 in smaller
03Sofa height from the floor to the top of the back, so the calculator knows whether standing it fully on end is an option
04Door clear opening width between the inside faces of the stops with the door open
05Whether the back cushions and feet come off, both of which change the diagonal

Don't make these

Common mistakes.

Most “it didn't fit” stories trace back to one of these oversights.

⚠Measuring the diagonal along the fabric contour instead of as a straight line. The line is what matters, because the doorway does not follow the upholstery
⚠Taking the diagonal from the back top to the front top. The correct line runs to the front BOTTOM edge, which is a longer run and a smaller angle
⚠Measuring with the back cushions on. Take them off first, and the diagonal usually drops another 2 to 4 in
⚠Comparing the diagonal against the nominal door size instead of the clear opening, which is 1.5 to 2 in narrower
⚠Assuming a recliner has a usable diagonal. The mechanism is rigid, so a recliner often has to go through upright even when the numbers suggest a tilt

Frequently asked

Questions we keep getting.

What is diagonal depth?
Diagonal depth is the straight line measured from the highest point of a sofa back down to the front bottom edge of its base. When a sofa is tilted onto its side and carried through a doorway, that line is the profile passing through the opening, which is why it decides the fit rather than the sofa depth.
01
How do I calculate diagonal depth of a sofa?
Take the back cushions off. Hold a straight edge or a taut string from the top back corner of the frame to the front bottom edge of the base, keeping it straight rather than following the upholstery, and measure that line. On most three seater sofas it comes out 4 to 8 in less than the sofa depth.
02
Why is diagonal depth smaller than sofa depth?
Because the sofa is not a rectangle in profile. The back leans, the base is set back from the arm face, and the widest horizontal measurement across the piece is not the same as the shortest line through it when it is turned. Tilting takes advantage of that difference.
03
What diagonal depth do I need for a 30 inch door?
A 30 in door gives about 28.5 in of clear opening once the stops are counted. A diagonal depth under 28 in goes through with usable margin. Between 28 and 28.5 in it will go, but take the door off its hinges first, which buys about 2 more inches.
04
Does diagonal depth apply to sectionals?
Yes, but measure each piece separately. A sectional is delivered and moved as individual units, so the diagonal of the largest single piece is the number that has to clear the door. The assembled footprint never passes through anything.
05

Related guides

Related item guides & reading.

Couch/Sofa GuideStandard 3-seat couch dimensions, doorway clearance, stairway fit checks, and expert moving tips. Find out if your sofa will fit before moving day.Moving a Couch Through a Narrow Doorway: Complete GuideYour couch is wider than your door. Here are 7 proven techniques to get it through — from tilting angles to door removal to the pivot-and-slide method.Complete Guide to Measuring Furniture for a MoveMost people measure width and call it done. Moving requires 6 measurements per item — plus path measurements. Here's the complete measurement protocol.

Related fit checks.

Will a Couch Fit Through a Door?Free calculator checks if your couch or sofa fits a 28, 30, 32, or 36-inch doorway. Enter dimensions for an instant pass / tight-fit / fail verdict and the best tilt angle.Will a Sectional Fit Through a Door?Check if your sectional sofa will fit through a doorway. Measure individual sections, account for connectors, and plan your approach piece by piece.Will a Recliner Fit Through a Door?Check if a recliner will fit through a doorway. Measure recliner width, depth, removable back, footrest latch, and door clear opening before moving or delivery.Will a Couch Fit Around a Hallway Corner?Check if your couch will fit around a hallway corner. Calculate the turning radius needed for L-shaped and T-shaped corridor turns.Will My Sofa Fit Through the Door? CalculatorFree sofa fit calculator. Enter your sofa and doorway and get an instant verdict, the tilt that works, and the diagonal depth that actually decides it.

All door fit checks →

Unlock stair simulation, AR visualization, and more.

Will it fit? Know before you buy.

Get a verdict in seconds — then test every angle until you’re sure.

Open the fit calculator

ItemFits

About Blog FAQ Features Pricing Work with us

Home / Doorway & Entry Clearance

Sofa Diagonal Depth Calculator

Diagonal depth is what passes through the doorway when a sofa is tilted, and it is smaller than the sofa depth.

Trusted across thousands of fit checks · updated daily

400 questions answered

Room Preview·Visual Results·Simulations

Fit summaryFIG. CLEARANCE

Whether it fits comes down to the measurements most people skip.

The tilted profile, not the sofa depth, is what has to clear the stops.

The spaceInterior door 28 to 30" clear. Bedroom door 30 to 30.5" clear. Entry door 34 to 36" clear

What decides itDiagonal depth vs. door clear opening width

What to measureStandard three seater sofa: 35 to 38" deep, diagonal depth about 26 to 30". Loveseat: 34 to 36" deep, diagonal about 25 to 28". Measure yours for an exact verdict

Real openings run about 1 to 2 inches under the labeled size, and a single inch can flip the result. Check your own measurements before you buy or move.

ReferenceDoor Guide Furniture Dimensions Door Sizes by Country

About 10 seconds · no signup

Verdicts compare all six item orientations against the space using verified building standards. See our methodology

10,000+ fit checks run·Last check: a few minutes ago

“Checked my mattress before ordering. Tight fit, but it worked with the door removed.” — Online shopper

Measure smart

What to measure.

Four numbers decide nearly every fit check. Get these right and the rest follows.

01Diagonal depth: hold a straight edge from the highest point of the sofa back down to the front bottom edge of the base, and measure that straight line. It is the profile that passes through a doorway when the sofa is tilted
02Sofa depth for comparison, measured horizontally from the back to the front edge. Expect the diagonal to come out 4 to 8 in smaller
03Sofa height from the floor to the top of the back, so the calculator knows whether standing it fully on end is an option
04Door clear opening width between the inside faces of the stops with the door open
05Whether the back cushions and feet come off, both of which change the diagonal

Don't make these

Common mistakes.

Most “it didn't fit” stories trace back to one of these oversights.

⚠Measuring the diagonal along the fabric contour instead of as a straight line. The line is what matters, because the doorway does not follow the upholstery
⚠Taking the diagonal from the back top to the front top. The correct line runs to the front BOTTOM edge, which is a longer run and a smaller angle
⚠Measuring with the back cushions on. Take them off first, and the diagonal usually drops another 2 to 4 in
⚠Comparing the diagonal against the nominal door size instead of the clear opening, which is 1.5 to 2 in narrower
⚠Assuming a recliner has a usable diagonal. The mechanism is rigid, so a recliner often has to go through upright even when the numbers suggest a tilt

Frequently asked

Questions we keep getting.

What is diagonal depth?
Diagonal depth is the straight line measured from the highest point of a sofa back down to the front bottom edge of its base. When a sofa is tilted onto its side and carried through a doorway, that line is the profile passing through the opening, which is why it decides the fit rather than the sofa depth.
01
How do I calculate diagonal depth of a sofa?
Take the back cushions off. Hold a straight edge or a taut string from the top back corner of the frame to the front bottom edge of the base, keeping it straight rather than following the upholstery, and measure that line. On most three seater sofas it comes out 4 to 8 in less than the sofa depth.
02
Why is diagonal depth smaller than sofa depth?
Because the sofa is not a rectangle in profile. The back leans, the base is set back from the arm face, and the widest horizontal measurement across the piece is not the same as the shortest line through it when it is turned. Tilting takes advantage of that difference.
03
What diagonal depth do I need for a 30 inch door?
A 30 in door gives about 28.5 in of clear opening once the stops are counted. A diagonal depth under 28 in goes through with usable margin. Between 28 and 28.5 in it will go, but take the door off its hinges first, which buys about 2 more inches.
04
Does diagonal depth apply to sectionals?
Yes, but measure each piece separately. A sectional is delivered and moved as individual units, so the diagonal of the largest single piece is the number that has to clear the door. The assembled footprint never passes through anything.
05

Related guides

Related item guides & reading.

Related fit checks.

All door fit checks →

Unlock stair simulation, AR visualization, and more.

Will it fit? Know before you buy.

Get a verdict in seconds — then test every angle until you’re sure.

Open the fit calculator