{{ resultsReady ? 'Picture area: B compared with A' : 'Check the screen measurements' }}

Screen A

Viewable diagonal A:{{ params.d1 }} {{ params.unit }}

Aspect ratio A:

Custom ratio A:

Screen B

Viewable diagonal B:{{ params.d2 }} {{ params.unit }}

Aspect ratio B:

Custom ratio B:

Screen C

Viewable diagonal C:{{ params.d3 }} {{ params.unit }}

Aspect ratio C:

Custom ratio C:

Screen D

Viewable diagonal D:{{ params.d4 }} {{ params.unit }}

Aspect ratio D:

Custom ratio D:

Screen A resolution:

Optional. Enter pixel width and height for PPI; the selected ratio still controls geometry.

×px

Screen B resolution:

Optional. Enter pixel width and height for PPI; the selected ratio still controls geometry.

×px

Screen C resolution:

Optional. Enter pixel width and height for PPI; the selected ratio still controls geometry.

×px

Screen D resolution:

Optional. Enter pixel width and height for PPI; the selected ratio still controls geometry.

×px

Eyes-to-screen distance:

Optional. Measure from your eyes to the screen.

Viewing reference:

Horizontal angle reference; seating range spans 40° to 30°.

Available picture width:

Optional pair. The frame allowance is added on all four edges.

Available picture height:

Enter both dimensions. Picture plus allowance fits at equality.

Frame allowance per edge:

Optional. Blank uses 0. Adds this much to every edge for frame or clearance; equality counts as fitting.

Equivalent sizes preserve:

Blank uses picture height. Choose width or area to compare different screen shapes on that basis.

Geometry units:

Converts physical inputs while preserving the same screen sizes.

Decimal places:

Blank uses one decimal. CSV retains full precision.

Screen	Width ({{ params.unit }})	Height ({{ params.unit }})	Area ({{ params.unit }}²)	Area vs A (%)	Copy
Screen {{ row.id }}	{{ fmt(row.width) }}	{{ fmt(row.height) }}	{{ fmt(row.area) }}	{{ signed(row.percent) }}%

Screen	Width Δ ({{ params.unit }})	Width Δ (%)	Height Δ ({{ params.unit }})	Height Δ (%)	Area Δ ({{ params.unit }}²)	Copy
Screen {{ row.id }}	{{ signed(row.width) }}	{{ signed(row.width_percent) }}%	{{ signed(row.height) }}	{{ signed(row.height_percent) }}%	{{ signed(row.area) }}

Check	Result	Copy
{{ row.label }}	{{ row.value }}

Target ratio	{{ screen.id }} · same {{ equivalentMatch }} ({{ params.unit }})	Copy
{{ row.ratio }}	{{ fmt(value.diagonal) }}

Chart unavailable. Placement distances remain available.

Calculation method

{{ row.label }}{{ row.value }}

Similar tools

A TV or monitor's viewable diagonal is the distance between opposite picture corners. A marketed size class may round that measurement. Width and height also depend on screen shape, so a larger diagonal can still mean a shorter picture.

A rectangular picture with its corner-to-corner diagonal, horizontal width and vertical height marked inside a surrounding frame. — Picture dimensions exclude the surrounding frame.

Aspect ratio describes width relative to height. A 16:9 picture is 16 units wide for every 9 units of height. At the same diagonal, 16:10 and 4:3 shapes provide more height than 16:9, while wider shapes such as 21:9 and 32:9 trade some height for horizontal space. This is why an ultrawide monitor's diagonal can sound like a much larger upgrade than its picture height suggests.

Picture area also grows faster than the diagonal. When the aspect ratio stays the same, increasing the diagonal by 10% increases both width and height by 10%, producing 21% more area. Across different ratios, the shape must also be included in the calculation. Equal diagonals do not guarantee equal areas.

The useful comparison depends on where the screen will go and what it will replace.

A TV for a room needs enough wall or cabinet space, together with a suitable picture width for the seating distance. A picture that fits a recess may still belong to a television whose frame or stand does not fit.
A monitor for a desk needs usable width and height at the actual working distance. Resolution and display scaling also affect how much text and how many windows can be shown at a readable size.
An ultrawide replacing two monitors should be compared by height and combined width. Two identical 16:9 pictures placed side by side form a 32:9 rectangle before allowing for bezels or a gap. The diagonals of the two monitors cannot simply be added to obtain the diagonal of that combined rectangle.

Resolution counts pixels across and down the picture. Pixel density, expressed as pixels per inch (PPI), relates those counts to physical size. Enlarging a screen without adding pixels lowers its PPI. Viewing distance changes how large the pixels appear, so PPI alone cannot predict perceived detail or text readability. Higher resolution can support finer detail while scaling keeps text and controls large enough to use.

Seating distance changes the horizontal angle occupied by the picture. A wider screen or a closer seat produces a larger angle. Cinema-derived viewing references provide starting points for planning a room, but preferences and viewing tasks still matter. Calculated picture dimensions and seating angles are estimates from the supplied dimensions, not measurements of an actual device or an assessment of eye health.

How to Use This Tool:

The starting comparison is 55 inches against 65 inches, both at 16:9. Results update as you edit. For centimetres, select Geometry units under Advanced; changing units converts the physical values already entered.

Enter the viewable diagonal and physical aspect ratio for each candidate. Keep the reference screen in Screen A. Use Add screen to compare up to four candidates, or choose Custom ratio and enter its width and height parts.
Enter both pixel dimensions under Screen A resolution and the corresponding fields for other screens if you want PPI. Use the native pixel resolution from the manufacturer's specifications.
Enter both Available picture width and Available picture height for a fit check. Set Frame allowance per edge to the frame or clearance amount you want added on every edge. Blank means zero.
Enter Eyes-to-screen distance to compare the candidates from your seat. Measure to the centre of the screen from a position directly in front of it. Select a Viewing reference only if you also want a target comparison and a diagonal calculated for that target.
Review any highlighted fields before relying on the affected result. Invalid diagonals or ratios stop the main comparison; an invalid optional value can leave picture dimensions available while its dependent check is withheld.
The message Fit withheld: correct the frame allowance. means you must enter a valid allowance. Clear it only when you intend to use zero allowance.

Interpreting Results:

The headline percentage compares Screen B's picture area with Screen A. Every candidate's differences are measured against A, including Screens C and D. More area can come mainly from extra width, so check the individual width and height when the shapes differ.

The outlines share one relative scale. They show differences in shape and size, but they are not a life-size display or a ruler for measuring your current screen.
In Placement guide, remaining width and height are the total unused amounts after the allowance is included. A negative amount identifies the shortfall. A fitting result covers the calculated picture and your allowance; confirm the manufacturer's full device dimensions, stand footprint, mounting depth and required clearances before buying.
Meets target means the horizontal angle is at least the selected reference. It has no upper-angle limit, so a very close seat can also meet it. Use the curves and seat markers in Viewing angles to compare possible positions; the label does not establish comfort or certify a room.
Equivalent sizes gives the diagonal needed at the listed aspect ratios while preserving a chosen measurement. The default preserves picture height. Select width or area under Equivalent sizes preserve when either is the constraint that matters. An equivalent diagonal is a calculated size, not a promise that a matching product exists.

CSV values retain calculation precision, so they can show more digits than the displayed tables. DOCX tables follow the selected decimal places.

Technical Details:

A flat rectangular picture forms a right triangle with its width, height and diagonal. Its aspect ratio fixes the relationship between the two sides, allowing the diagonal to determine both dimensions. Curvature, an angled viewing position and the physical shape of the surrounding device are outside this rectangular model.

Formula Core

Let d be the viewable diagonal, a:b the width-to-height ratio, W the picture width, H the picture height and S the picture area. The Pythagorean relationship gives the dimensions and area below.

\begin{array}{l} W = \frac{d \times a}{\sqrt{a^{2} + b^{2}}} \\ H = \frac{d \times b}{\sqrt{a^{2} + b^{2}}} \\ S = W \times H = \frac{d^{2} \times a \times b}{a^{2} + b^{2}} \end{array}

All lengths in an equation must use the same unit. One inch is exactly 2.54 cm, so one square inch is 6.4516 cm². For a 65-inch 16:9 picture, substituting 65, 16 and 9 gives approximately 56.65 inches of width, 31.87 inches of height and 1805.34 in² of picture area.

Changes relative to Screen A

For a width, height or area X, the reference value X_A belongs to Screen A. Absolute differences retain the original unit; percentage differences divide by A's value.

\begin{array}{l} ΔX = X - X_{A} \\ Percentage change = 100 \times (\frac{X}{X_{A}} - 1) \end{array}

At a fixed aspect ratio, width and height grow in direct proportion to the diagonal, while area grows with its square. The 55-inch to 65-inch comparison therefore increases width and height by about 18.18% and area by about 39.67%. Reversing A and B changes the percentage because it changes the denominator.

Pixel density and exact aspect ratios

For square pixels, pixel density follows from the diagonal pixel count divided by the physical diagonal in inches. Here x and y are the horizontal and vertical pixel counts, and d_in is the viewable diagonal expressed in inches. PPI remains pixels per inch when the other dimensions are displayed in centimetres.

PPI = \frac{\sqrt{x^{2} + y^{2}}}{d_{in}}

The pixel ratio must agree with the selected physical ratio for that square-pixel calculation to be meaningful. PPI is withheld when the absolute relative difference between the pixel width-to-height ratio and the selected ratio exceeds 0.000001, or when either pixel dimension is missing or invalid. The selected aspect ratio continues to determine physical geometry.

A commercial 21:9 label may describe a family of ultrawide shapes. Exact 3440 × 1440 reduces to 43:18, while 2560 × 1080 reduces to 64:27. Neither is exactly 21:9.

Viewing angle and seating distance

The horizontal viewing angle spans the left and right edges of the picture as seen from a centred position. It differs from a manufacturer's off-axis viewing-angle specification. Let D be the perpendicular eyes-to-screen distance and θ the horizontal angle in degrees. These equations calculate the angle, the distance for a chosen angle and the diagonal needed at that distance.

\begin{array}{l} θ = \frac{360}{π} \times \arctan (\frac{W}{2 \times D}) \\ D = \frac{W}{2 \times \tan (\frac{π \times θ}{360})} \\ d_{target} = \frac{2 \times D \times \tan (\frac{π \times θ}{360}) \times \sqrt{a^{2} + b^{2}}}{a} \end{array}

The factors involving π convert degrees to and from radians. Wider pictures require greater distance to occupy the same angle. Each reference below has a different origin and should retain that context.

Origins and interpretation of the three horizontal viewing-angle references
Angle	Reference	Meaning and limit
30°	Historical SMPTE guidance	EG 18-1994 discussed approximately 30° horizontally. It was withdrawn in 2003 and is no longer endorsed by SMPTE.
36°	THX cinema screen placement	THX recommends a 36° horizontal viewing angle from the farthest auditorium seat. This is cinema guidance.
40°	Approximation of THX home-TV sizing	THX's distance rule divides the diagonal by 0.835. For a 16:9 picture, the geometric angle is about 39.99°, rounded here to 40°.

Reference-distance calculations use exactly 30°, 36° and 40°. The seating range runs from the closer 40° distance to the farther 30° distance; it is a planning interval rather than a comfort or visual-acuity test. Applying a fixed angle to another aspect ratio remains valid geometry, but the 0.835 diagonal rule does not imply the same horizontal angle for every shape.

A 65-inch 16:9 picture has a calculated 40° to 30° range of about 77.83 to 105.71 inches. From 96 inches, or 8 feet, it occupies about 32.88°. Reaching 36° at that position would require about a 71.58-inch 16:9 diagonal.

Picture fit with an allowance

Let c be the allowance on each edge, and U and V the available width and height. Adding the allowance on both sides increases each required dimension by twice c. Both inequalities must hold for a fit, including equality.

W + 2 c \leq U and H + 2 c \leq V

Subtracting the required width and height from U and V gives the remaining space. The largest fitting diagonal at the same aspect ratio is limited by whichever available dimension runs out first.

d_{max} = \max (0, \min (\frac{U - 2 c}{a}, \frac{V - 2 c}{b}) \times \sqrt{a^{2} + b^{2}})

The same allowance applies to all four edges and all candidates. It cannot reproduce asymmetric bezels or a stand's footprint. If the allowance consumes the available space, the largest fitting diagonal is zero.

Equivalent diagonals across shapes

A new shape can preserve width, height or area, but these are different comparisons. For a target aspect ratio r expressed as width divided by height, the following diagonals preserve the selected quantity.

\begin{array}{l} d_{same width} = \frac{W \times \sqrt{r^{2} + 1}}{r} \\ d_{same height} = H \times \sqrt{r^{2} + 1} \\ d_{same area} = \sqrt{\frac{S \times (r^{2} + 1)}{r}} \end{array}

Input limits and numerical precision

Viewable diagonals accept 1 to 200 inches, or 2.54 to 508 cm. Custom ratio parts each accept 0.01 to 10000. Pixel dimensions must be whole numbers from 1 to 32768. Entered distance and available dimensions accept 0.0000001 to 10000 inches, or 0.000000254 to 25400 cm. The per-edge allowance accepts 0 to 100 inches, or 0 to 254 cm.

Display precision is zero, one or two decimal places, with one decimal by default. Calculations and comparisons use unrounded values, so displayed rounding never decides whether a picture fits or an angle reaches a target. Fit and target comparisons include tolerances of 10⁻¹⁰ inch and 10⁻¹⁰ degree respectively to absorb numerical roundoff; these provide no practical clearance.

More digits do not make an advertised diagonal or an approximate room measurement more accurate. Use the manufacturer's actual viewable diagonal when it differs from the marketed size class.

Privacy Notes:

Calculations run in your browser using measurements you enter. They do not scan or calibrate your display and do not request camera, microphone, location or screen-capture access. Inputs and settings are carried in the page address, so sharing that address shares the comparison. The viewing chart loads an external resource when opened.

Worked Examples:

The figures below use inches and two decimal places.

Replacing a 27-inch monitor with an ultrawide

A 27-inch 16:9 picture is about 23.53 × 13.24 inches. A 34-inch 43:18 picture is about 31.36 × 13.13 inches, giving much more width with almost the same height. With height preserved, Equivalent sizes gives the ultrawide a 16:9 equivalent of about 26.78 inches. For a 3440 × 1440 resolution, select 43:18 to obtain about 109.68 PPI. Selecting nominal 21:9 instead produces Ratio mismatch; PPI withheld; correcting the physical ratio restores the PPI calculation.

A picture fits until the frame allowance is included

Compare a 65-inch 16:9 picture with an available space of 57 × 33 inches. With zero allowance it fits. An allowance of 0.5 inch per edge raises the required dimensions to about 57.65 × 32.87 inches, so the result becomes Picture plus allowance does not fit. At two decimal places, the remaining width reads -0.65 in and the remaining height reads 0.13 in. The largest fitting 16:9 diagonal is about 64.25 inches under those assumptions. A smaller candidate or a wider space is needed before checking its actual device dimensions.

References:

EG 18-1994: Design of Effective Cine Theaters, Society of Motion Picture and Television Engineers, 1994; withdrawn March 26, 2003.
THX FAQ: cinema screen placement and home viewing, THX.
SI Units – Length, National Institute of Standards and Technology, updated September 19, 2025.
How is the Screen Size of a Television Determine?, TCL.
4K resolution and pixel density, EIZO.
Dell S 34 USB-C Monitor S3425DW User’s Guide, Dell, March 2026, Rev. A01.

Screen Size Comparison

{{ resultsReady ? 'Picture area: B compared with A' : 'Check the screen measurements' }}

Screen A

Screen B

Screen C

Screen D

Calculation method

Similar tools

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core

Changes relative to Screen A

Pixel density and exact aspect ratios

Viewing angle and seating distance

Picture fit with an allowance

Equivalent diagonals across shapes

Input limits and numerical precision

Privacy Notes:

Worked Examples:

Replacing a 27-inch monitor with an ultrawide

A picture fits until the frame allowance is included

References: