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CalcMax

Aspect Ratio Calculator

Range: 1 – 1,000,000

Range: 1 – 1,000,000

Range: 1 – 1,000,000

Range: 1 – 1,000,000

Result

720.0000

New height

New width
1,280.0000
Multiplier (new ÷ original)
0.6667

An aspect ratio calculator scales a size up or down while keeping the same shape: 1920 × 1080 with a new width of 1280 has a height of 720, because both pairs divide down to the same ratio. Type the original width and height — the shape you are keeping — then either the new width or the new height, and the panel works out the one you left blank. The four numbers are two ways of writing the same proportion, which is why filling in three of them is enough, and why filling in all four is only accepted when the fourth agrees with the other three. Nothing here carries a unit. 1920 × 1080, 16 × 9 and 1.85 × 1 all work, and the answer is in pixels, millimetres or inches depending on what you typed, because the only thing being used is the proportion between the numbers. That is what makes the page useful for a photo that has to fit a frame, a video that has to be resized for a platform's limit, or a print that has to keep its shape at a different size. The multiplier beside the two sizes says how much the new size is of the original in one number: 0.6667 means the new size is about two thirds of the original, and a figure above 1 means it was scaled up. It is the same figure whichever pair you look at, which is another way of saying the shape did not change. Scaling only moves the numbers along that fixed proportion, so the reduction and the enlargement are the same calculation: going from 1920 wide down to 1280 and going from 1920 wide up to 3840 are both solved by multiplying by the ratio of the widths. A width and a height that do not agree with it are not accepted silently — if all four numbers are given and the pairs do not match, the panel says so rather than printing one of them as if it were the answer, and that is also how you check whether two sizes are the same shape without doing the division yourself. A zero is refused anywhere, because a side of zero has no ratio: the proportion needs both sides positive, and so does the division that solves the fourth number. If what you want is the ratio itself written in its smallest form as 16:9, or as a decimal figure, that is a different question and a different page; this one answers how big the other side is.

Common sizes scaled by their aspect ratio

Original widthOriginal heightNew widthNew height
192010801280720
19201080853.3333480
192010801000562.5
1440108019201440
10801920540960
10801080500500
2560144019201080
1920108038402160

Every row is solved by the same proportion, and no row is a special case of it. The first row is the default pair, 1080p scaled down to the width of a 720p frame. The second row is the other direction: the height was given as 480 and the width came out at 853.3333, which is the row that shows why the panel prints four decimal places — the answer does not divide exactly. The third row is a width of 1000 giving a height of 562.5, another inexact one, and the fourth row is a 4 : 3 frame scaled up, with both sides larger than the original. The fifth row is a phone-shaped 9 : 16 portrait frame, where the width is the smaller side and the multiplier is above 1 because the width grew from 1080 to 2160. The sixth row is a square, the one ratio where the new width and the new height always come out equal. The seventh row gives the height again, this time asking how wide a 1440p frame is at a height of 1080. The last row is an enlargement to 4K, which is the same multiplication as the first row with a factor above 1. Read together, the rows show that reduction and enlargement are one operation, that a given ratio can be written in whole numbers or in decimals, and that the answer is often not a whole number even when both inputs are.

Formula

Original width ÷ original height = new width ÷ new height New width = original width × new height ÷ original height Multiplier = new width ÷ original width

Original width and height
The shape being kept, as the two numbers of the ratio you already have: 1920 and 1080 for a 1080p frame. Both are required, and neither may be zero, because they are the ratio the whole page is about.
New width or new height
One side of the size you are scaling to, and the one number the rest is solved from. Give the width to get a height, or the height to get a width; the panel fills in whichever you left out. Both may be given as well, in which case they have to agree with the original ratio.
The proportion
Original width ÷ original height equals new width ÷ new height. That single equation is the whole calculation, and it is why three of the four numbers are enough to fix the fourth — and why a fourth that does not fit is rejected rather than quietly overridden.
Multiplier
The new size as a multiple of the original: new width ÷ original width, or equivalently new height ÷ original height. Below 1 means a reduction, above 1 an enlargement, and it is the same figure for the width and for the height because the shape is unchanged.
Rounding
Every figure on the panel is rounded to four decimal places. The width and the height are both divisions, so an exact answer is often not available: scaling 1920 × 1080 to a width of 853 gives a height of 479.7375, and four places keep the two figures consistent with each other.

The first use is a photo or an image that has to be fitted into a fixed space: the frame is 1280 wide, you have a 1920 × 1080 original, and you need the height before you can resize it. The second is a platform limit that constrains one side only — a video has to be 1080 high, or a thumbnail 500 wide — and the other side has to follow or the picture stretches. The third is a print at a different size: a poster that has to keep the shape of a 4 × 3 photo scales both sides by the same factor, and the multiplier tells you what that factor is before you commit to it. The fourth is checking someone else's numbers: put in both pairs and see whether they agree, which answers whether a 1280 × 700 file is really the same shape as 1920 × 1080 without working out either division. The fifth is planning an enlargement, where the multiplier is the figure worth reading first — 2 means four times the area, which is usually the number that decides whether a photo can be blown up at all.

Worked examples

  1. 1920 × 1080 scaled to a width of 1280

    1. The proportion: 1920 ÷ 1080 = 1280 ÷ new height
    2. Solve for the height: 1080 × 1280 ÷ 1920 = 720
    3. Multiplier: 1280 ÷ 1920 = 0.6667
    4. Check: 1920 ÷ 1080 = 1.7778 and 1280 ÷ 720 = 1.7778 — the same shape

    The default case, and the one most people arrive with: a 1080p image being scaled down to 720p, where the width of 1280 is the well-known partner of a height of 720. The multiplier below 1 says it is a reduction, and both sides were multiplied by the same factor, which is what keeps the picture from being stretched.

  2. 1920 × 1080 scaled to a height of 480

    1. The proportion: 1920 ÷ 1080 = new width ÷ 480
    2. Solve for the width: 1920 × 480 ÷ 1080 = 853.3333
    3. Multiplier: 853.3333 ÷ 1920 = 0.4444
    4. The height was given and the width was solved, which is the other direction

    The half of the page the card describes as or height: a platform gives you a height and you need the width. The answer does not divide exactly — 480 is not a whole fraction of 1080 in a way that keeps the width whole — and it is printed to four decimal places, which is why the panel rounds rather than pretending to be exact.

  3. 1920 × 1080 scaled up to a width of 3840

    1. The proportion: 1920 ÷ 1080 = 3840 ÷ new height
    2. Solve for the height: 1080 × 3840 ÷ 1920 = 2160
    3. Multiplier: 3840 ÷ 1920 = 2
    4. The same calculation as the first example, with the factor above 1 instead of below it

    Enlargement is not a separate operation: the proportion is the same one and only the multiplier changes sides. A multiplier of 2 doubles both sides, which quadruples the area — worth knowing before blowing an image up, since the file has four times as many pixels to fill.

  4. A 1.85 × 1 widescreen frame at a width of 1850

    1. The proportion: 1.85 ÷ 1 = 1850 ÷ new height
    2. Solve for the height: 1 × 1850 ÷ 1.85 = 1000
    3. Multiplier: 1850 ÷ 1.85 = 1000
    4. The ratio was written as decimals, and the result came out whole

    An aspect ratio does not have to be written in whole numbers: 1.85 : 1 is a widescreen film ratio, and 16 : 9 written as 1.7778 : 1 is the same kind of expression. The multiplier of 1000 is unusual only because the original side was 1; it says the same thing as any other multiplier, that both sides grew by that factor.

Limitations

Neither side of the original ratio may be zero, and a zero is refused in the new size as well, because a proportion with a zero side has no second number to solve. Four decimal places is the precision of every figure on the panel, so a width solved from a height is rounded: 1920 × 1080 at a height of 480 gives 853.3333 rather than the exact value, and asking for more precision than that is asking for a size no tool will honour anyway. The page does not simplify the ratio or print it in the form 16 : 9, and it does not give it as a decimal figure either: those are the questions a ratio calculator answers, and printing them here as well would put the same answer on two pages. All four numbers can be entered at once only when the fourth agrees with the other three, and a fourth that does not is refused rather than corrected, since silently overriding a number someone typed is worse than an error message. Only one ratio is handled at a time: comparing two different shapes, or converting a ratio into a physical size, needs the ratio itself in the first case and a paper size or a resolution in the second. Finally, the panel does not choose a print size, a resolution or a platform's recommended dimensions for you — it works out the side you left out, and the judgement about which size is right stays with you.

Frequently asked questions

How do I work out the new width or height for an aspect ratio?
Multiply the side you are scaling by the ratio of the new size to the original, or use the proportion directly: original width ÷ original height = new width ÷ new height. For 1920 × 1080 at a new width of 1280, the height is 1080 × 1280 ÷ 1920, which is 720.
Does it matter what unit the numbers are in?
No, and that is why the fields have no unit beside them. Only the proportion between the numbers is used, so pixels, millimetres and inches all give the same answer: 1920 × 1080 and 16 × 9 behave identically, and the result is in whatever unit you typed.
Can I put in the new height instead of the new width?
Yes — fill either one and the other is solved for you. That is what the second field is for: a limit that constrains the height, such as a 1080-high video, gives you the width you need without any rearranging on your part.
What does the multiplier mean?
It is the new size divided by the original, so 0.6667 means the copy is about two thirds the size and 2 means it was doubled. It comes out the same whether you work it from the width or the height, which is another way of saying the two sides were scaled by one common factor.
Why can I fill in all four numbers only sometimes?
Because the four are not independent: any three fix the fourth, so a fourth that does not agree with the other three describes a different shape. The panel refuses that combination instead of printing one of the numbers as if it were right — and checking a pair that way is a legitimate use, since it tells you whether two sizes are the same shape.
Can I enter a ratio like 1.85 : 1 instead of whole numbers?
Yes, and it is common for film and print sizes. Put 1.85 in the original width and 1 in the original height, then give the width you are scaling to; the height comes out of the same proportion as any other pair. Whole numbers are simply the easier case to type.
Where is the ratio itself, like 16 : 9?
This page scales a size and does not simplify the ratio, so it does not print 16 : 9 or the ratio as a decimal. That is the ratio calculator's answer, and it is one link away; this page keeps its own answer, which is how big the other side of the new size is.

References

Related calculators

Ratio CalculatorSimplify a ratio, with the per-one form and the decimal.Proportion CalculatorSolve a proportion for the missing term, with the steps.Equivalent Fractions CalculatorFractions equal to a given one, up to a limit.Screen Size CalculatorScreen dimensions and aspect ratio from a diagonal.