Photo Resize in CM – Resize Image in CM, Pixels & KB

How to Resize a Photo in CM

To resize a photo in cm, upload it above — the resizer is already set to 3.5 × 4.5 cm at 200 DPI — drag the crop box over the face and download. The photo is cropped to the exact shape, converted to the matching pixel size (276 × 354 px) and compressed under your KB limit.

1. Set the size in cm in Optional dimensions (or use the calculator and press Use this size).
2. Check the DPI — use the value the form gives; 200 DPI is a common default for online forms.
3. Choose the KB limit, for example 50 KB, or a range such as 20–50 KB.
4. Upload, adjust the crop box and download.

How CM Converts to Pixels

A centimetre is a printed length, while a digital photo is measured in pixels. DPI (dots per inch) links the two: it says how many pixels fit in one inch. Because 1 inch = 2.54 cm, the formula is:

pixels = cm ÷ 2.54 × DPI

So 3.5 cm at 200 DPI is 3.5 ÷ 2.54 × 200 ≈ 276 pixels, and 4.5 cm is ≈ 354 pixels. For millimetres divide by 25.4 instead of 2.54; for inches simply multiply by the DPI.

Higher DPI means more pixels and a sharper print — and a larger file. For online forms that only display the photo on screen, 200 DPI is plenty.

Resize Image in CM and KB Together

Forms often combine both rules: "3.5 × 4.5 cm, between 20 KB and 50 KB". The resizer handles them together:

• The cm size and DPI fix the pixel dimensions. Those are kept exactly.
• The KB limit is then met by adjusting JPEG quality only.
• Keep proportions crops the photo to the cm shape instead of stretching it, and the crop box lets you choose which part to keep.

A 3.5 × 4.5 cm photo at 200 DPI is usually 6–15 KB at high quality, so it fits easily under 50 KB. If a form needs at least 20 KB, use Range mode — or increase the DPI to 300 (413 × 531 px), which produces a larger file (usually 10–25 KB).

Set 20–50 KB range

Image Resize in Pixels and KB

If the form gives pixels instead of centimetres — for example "200 × 230 pixels, under 50 KB" — switch the unit to px and enter the numbers directly. Everything else works the same: the crop box takes that shape, the pixels are kept, and the KB limit is met through quality.

Passport Size Photo in CM

The 3.5 × 4.5 cm passport-size format is the most requested size on application forms. For a good result:

• Use a plain, light background and even light on the face.
• Position the crop box so the face fills most of the frame, with a little space above the head.
• Keep the head straight and both ears and eyes visible if the form asks for it.
• For printing at a studio, use 300 DPI (413 × 531 px) and a higher KB limit.

Official passport applications have their own detailed rules — always follow the instructions of the authority you are applying to.

Image Resizer in CM: Phone and PC Steps

This image resizer in cm works in any browser. It is already set to 3.5 × 4.5 cm at 200 DPI with a 50 KB limit — change any of those to match your form.

On a phone

1. Open Optional dimensions under the tool and check the unit is cm.
2. Enter the width and height from the form, for example 3.5 and 4.5.
3. Choose the DPI the form gives — 200 if it gives none.
4. Pick the KB rule: Max size, or Range if there is a minimum.
5. Tap Select photos, drag the crop box over the face and tap Download.

On a laptop or PC

1. Set cm, size and DPI as above.
2. Drag the photo onto the upload box or paste it with Ctrl + V.
3. Adjust the crop box with the mouse and download.

The result card shows the pixel size the cm values produced (for example 276 × 354 px), the file size in KB and the quality used.

Common Photo Sizes in CM and Pixels

Pixels are rounded to the nearest whole number. Enter the cm values and DPI in the tool and it calculates these for you.

Photo Size Reducer in CM and KB

A photo size reducer in cm and KB has to do three things in the right order:

1. Crop the photo to the shape of the cm size (3.5 × 4.5 is taller than wide), so nothing is stretched.
2. Scale it to the exact pixels the cm size and DPI produce.
3. Compress to the KB limit by adjusting JPEG quality only, so the pixel size stays exact.

Common combined rules and the expected sizes at good quality:

If the KB range cannot be met at the required pixels, the tool tells you instead of quietly changing the dimensions.

Image Resize in Pixel and KB

For an image resize in pixel and KB, set the unit to px and type the numbers exactly as the form gives them. Common pixel rules:

Set 20–50 KB range

Resize Image in KB and Pixels: Which Rule Wins?

When you resize an image in KB and pixels at the same time, the pixels are fixed and only the quality can move. That has two consequences:

• Small pixels + high KB minimum: the file may not get big enough. A 140 × 60 px image cannot reach 20 KB at any quality. Use Range and check whether the minimum or the dimensions are really mandatory.
• Large pixels + low KB maximum: quality has to drop a lot, and the photo may look blocky. A 2,000 × 2,000 px image at 50 KB is a poor result. Use the smallest pixel size the form accepts.

If the form gives only a KB limit, leave the dimensions empty: the tool then chooses the pixel size itself for the clearest result.

Which DPI Should I Choose?

Use exactly the DPI the form states. If it says only "3.5 × 4.5 cm" with no DPI, 200 is a safe default for upload and 300 for printing.

CM, MM and Inches

The unit menu offers cm, mm, inch and px. Conversions:

• 1 inch = 2.54 cm = 25.4 mm.
• 35 × 45 mm is the same as 3.5 × 4.5 cm.
• 2 × 2 inches is 5.08 × 5.08 cm.
• pixels = inches × DPI, or cm ÷ 2.54 × DPI, or mm ÷ 25.4 × DPI.

Pick the unit the form uses so you can type its numbers directly without converting.

Keep Proportions: Crop, Don’t Stretch

A phone photo is usually 3:4 or 9:16, while 3.5 × 4.5 cm is 7:9. Fitting one into the other means either cropping or stretching. With Keep proportions on (the default), the crop box takes the 7:9 shape and you choose which part of the photo to keep — the face stays natural. Turning it off squeezes the whole photo into the box, which distorts faces and can lead to rejection. Keep it on for photos.

Positioning the Face in a CM Crop

• Face (chin to top of hair) about 70–80% of the frame height.
• Small gap above the head; top of the shoulders at the bottom.
• Face centred left to right, looking straight at the camera.
• Plain light background with no shadows behind the head.

Drag the crop box to move it and use its corner handle to resize it. The box keeps the cm shape while you adjust.

Why Do Forms Give Photo Sizes in CM?

Photo rules come from the paper era: a passport-size photo was a 3.5 × 4.5 cm print glued to a form. Online forms kept the same description because people know it, even though a digital file has no physical size — only pixels. The DPI value is the bridge: it tells you how many pixels the old paper size should have. That is why "3.5 × 4.5 cm" on its own is incomplete, and why the tool asks for DPI as well.

Document Sizes in CM and Pixels

A full A4 page at 200 DPI is nearly 4 megapixels — too many for a 100 KB limit if the page is full of text (dense A4 text stays readable at about 650–900 px wide at 100 KB). If a form gives a page size and a small KB limit, use 150 DPI or the largest KB allowed, and check the text in the preview.

Printing a Photo at the Exact CM Size

A digital file has pixels, not centimetres. When you print it, the printing software decides how big it appears on paper. To get exactly 3.5 × 4.5 cm:

1. Resize here at 300 DPI (413 × 531 px) for a sharp print.
2. In the print dialog or photo-printing app, set the print size to 3.5 × 4.5 cm, or choose "actual size"/"100%" if the software reads the file’s resolution — not "fit to page".
3. Print a test on plain paper and measure with a ruler before using photo paper.

Photo shops can print several copies on one 4 × 6 inch (10 × 15 cm) sheet; give them the 300 DPI file and say the size you need.

How to Check a Photo’s Pixel Size

• On this page: the result line shows width × height in pixels.
• Windows: right-click → Properties → Details → Dimensions.
• Mac: open in Preview → Tools → Show Inspector.
• Android: Gallery → photo → Details (ⓘ) shows resolution on most phones.
• iPhone: Photos → swipe up or tap ⓘ to see the resolution.

3 × 4 cm vs 3.5 × 4.5 cm

Both are called "passport size" in different places. They have nearly the same shape (3:4 vs 7:9) but different pixel counts: 3 × 4 cm is 236 × 315 px at 200 DPI, while 3.5 × 4.5 cm is 276 × 354 px. Use exactly the numbers your form gives. If you have already made one and need the other, start again from the original photo rather than resizing the resized copy.

Taking a Photo That Fits a CM Crop

• Hold the phone upright (portrait), since most cm sizes are taller than wide.
• Stand about 1–1.5 metres away and zoom slightly, rather than holding the phone close; close-ups distort the nose and ears.
• Leave space around the head so the crop box has room to frame it.
• Plain light wall behind, about half a metre to a metre from your back to avoid shadows.
• Daylight from the front, no flash.

Using the CM to Pixel Calculator

The calculator on this page converts any cm, mm or inch size to pixels at the DPI you choose. Enter the size, pick the DPI, and press Use this size to copy it into the resizer’s Optional dimensions. It is useful for checking a form’s requirement before you start — for example, to see that 5 × 7 cm at 300 DPI is 591 × 827 pixels.

Resizing a Printed Photo to a CM Size

If you only have a printed photo, photograph it flat in daylight from directly above, with no glare. Upload it, set the cm size and DPI, and drag the crop box to the photo itself, excluding the print’s white border. Because the photo of a print has extra texture, a slightly lower DPI (200 rather than 300) often looks cleaner for uploads.

Photos of Children and Babies

Children rarely sit still, so take several photos in good light and pick the sharpest. For babies, lay them on a plain white sheet and photograph from above — the sheet becomes the background. The cm crop lets you frame the face afterwards, so it does not matter if the original is not perfectly centred. Always check the specific rules for the document you are applying for.

Troubleshooting CM and Pixel Uploads

Common CM Resizing Mistakes

1. Forgetting the DPI — 3.5 × 4.5 cm at 72 DPI is only 99 × 128 px, far too small.
2. Typing cm values while the unit is set to px (or the reverse).
3. Turning off Keep proportions and stretching the face.
4. Resizing an already-resized copy instead of the original.
5. Using 600 DPI for an upload with a 50 KB limit.
6. Including the white border of a printed photo in the crop.

CM Resize Checklist

1. Read the form: cm (or mm/inch), DPI, KB rule, background colour.
2. Set the unit, size and DPI under Optional dimensions.
3. Choose Max size or Range for the KB.
4. Upload and position the crop box: face 70–80% of the height.
5. Check the result line: pixels, KB and quality.
6. Download and upload the new file.

Terms Used on This Page

DPI (dots per inch)

How many pixels fit in one inch. It links cm to pixels.

Pixels (px)

The dots that make up a digital image. Forms check these, not cm.

Keep proportions

Crops the photo to the target shape instead of stretching it.

Aspect ratio

Width divided by height. 3.5 × 4.5 cm is 7:9.

Passport size

Usually 3.5 × 4.5 cm; some forms use 3 × 4 cm or 2 × 2 inches.

Three CM Jobs, Step by Step

1. "Photo 3.5 × 4.5 cm, 20–50 KB, JPG"

1. Keep cm, 3.5 × 4.5 and 200 DPI.
2. Choose Range 20–50.
3. Upload, position the face and download — 276 × 354 px, raised into the 20–50 KB range with higher quality.

2. "Photo 35 × 45 mm at 300 DPI, max 100 KB"

1. Set the unit to mm, enter 35 and 45, choose 300 DPI.
2. Max size 100.
3. Download a 413 × 531 px JPG of about 10–25 KB.

3. "Photo 2 × 2 inches, 600 × 600 to 1200 × 1200 px, max 240 KB"

1. Set the unit to inch, enter 2 × 2 and 300 DPI (600 × 600 px).
2. Max size 240.
3. Choose the Square crop and download a 600 × 600 JPG of about 30–70 KB.

Photo Sizes in MM

Photo Sizes in Inches

For inches the formula is simplest: pixels = inches × DPI.

Worked Examples of the CM Formula

• 4 × 6 cm at 200 DPI: 4 ÷ 2.54 × 200 = 315 px; 6 ÷ 2.54 × 200 = 472 px → 315 × 472.
• 5 × 7 cm at 300 DPI: 5 ÷ 2.54 × 300 = 591; 7 ÷ 2.54 × 300 = 827 → 591 × 827.
• 3.5 × 1.5 cm signature at 200 DPI: 276 × 118.
• Reverse — pixels to cm: cm = pixels ÷ DPI × 2.54. A 600 px wide image at 300 DPI prints 5.08 cm wide.

When the Original Is Smaller Than the CM Size Needs

If your photo has fewer pixels than the cm size requires — for example a 300 × 400 px image for 3.5 × 4.5 cm at 300 DPI (413 × 531 px) — the tool enlarges it to the exact pixels. The result passes the dimension check but cannot be sharper than the original. For prints especially, start from a larger original; for uploads, 200 DPI (276 × 354 px) may already be met without enlargement.

Signatures and Thumb Impressions in CM

Signature rules often come in cm, typically 3.5 × 1.5 cm. Switch the crop to Signature, set the unit to cm, enter 3.5 × 1.5 and the DPI. At 200 DPI that is 276 × 118 px, usually 5–10 KB. For a 10–20 KB rule, choose Range 10–20; if the minimum cannot be met at those pixels, try 300 DPI (413 × 177 px). The signature resize page covers signatures in depth.

Resizing Several Photos to the Same CM Size

Select several photos at once and they are all resized to the same cm size, DPI and KB rule. Each photo gets its own crop box, so check each preview and move the box where needed. Download individually or as one ZIP — useful for families, schools and service centres preparing many photos to the same specification.

Private and Offline

The cm resizer runs entirely in your browser. Photos are not uploaded, stored or shared, and the page works without internet once loaded. The downloaded file contains only the image — camera details and GPS location are removed.

CM Resize in One Line Each

• Formula: pixels = cm ÷ 2.54 × DPI.
• Default DPI: 200 for uploads, 300 for prints.
• Passport size: 3.5 × 4.5 cm = 276 × 354 px (200 DPI) or 413 × 531 px (300 DPI).
• Shape: keep proportions on and crop; never stretch a face.
• KB: met through quality, with pixels kept exact.

Background and Appearance Rules

Size is only one part of a photo rule. Forms that give cm sizes usually also ask for:

• Background: most often white or off-white; some accept light blue or light grey. A plain wall works best.
• Expression: neutral, mouth closed, eyes open and looking at the camera.
• Head position: straight, not tilted; face centred.
• Glasses and headwear: many forms ask for no glasses and no caps, except headwear worn for religious reasons. Check your form’s rules.
• Recency: often a photo taken in the last few months.
• No edits: no filters, beauty modes or background replacement.

The resizer handles the size, shape and KB; the appearance rules depend on the photo you take.

Screen vs Print: Why the Same CM Size Has Different Pixels

On a screen, a 276 × 354 px photo and a 413 × 531 px photo can look the same size — the form decides how large to display it. On paper, both can print at 3.5 × 4.5 cm, but the 413 × 531 px one is sharper because it packs more dots into each centimetre. That is the whole reason DPI exists: for uploads, the form’s DPI defines the pixel count it checks; for prints, a higher DPI means a crisper photo. When a form gives no DPI and the photo is only for upload, 200 DPI keeps files small and clear.

Studio Photo or Do It Yourself?

A photo studio controls lighting and background and can print to exact sizes — worth it for official passports and visas with strict rules. For most online forms, a phone photo taken against a plain wall in daylight, cropped and resized here, is just as acceptable and takes a couple of minutes. If you have a studio print but need a digital file, ask the studio for the digital copy; it will be sharper than photographing the print.

What Happens When You Resize in CM

1. Convert: the cm (or mm/inch) size and DPI are turned into exact pixels.
2. Shape: the crop box takes the same proportions, and you position it on the photo.
3. Scale: the cropped area is resized to exactly those pixels with high-quality smoothing.
4. Compress: JPEG quality is searched, measuring each result to the byte, until the file meets your Max size or Range.
5. Clean: camera details and location are removed, and the result is shown with its pixels, KB and quality.

It all happens in your browser in a fraction of a second.

Different Forms, Different CM Rules

Even "passport size" varies: 3.5 × 4.5 cm is common in India and many countries, 2 × 2 inches is used for some visa and foreign applications, and 3 × 4 cm appears on some local forms. Pixel and KB limits vary too. Always take the numbers from the form or official notification you are filling, enter them exactly, and keep the original photo so you can produce another version if a second form asks for a different size. For exam-specific sizes, follow the official notification.

Typical File Sizes by CM Size

Plain backgrounds land at the low end, detailed photos at the high end. If your form’s KB minimum is above these numbers, use Range or a higher DPI if allowed.

Works on Every Device

The cm resizer works in any modern browser on Android, iPhone, iPad, Windows, Mac and Chromebook. On phones, Optional dimensions sits just below the photo; on larger screens it sits beside the preview. Your last-used unit and DPI stay selected while the page is open, so preparing several photos with the same rule is quick.

CM Rules Without a KB Rule (and the Reverse)

If a form gives only a cm size, choose a generous KB limit (for example 100 KB) so quality stays high; the cm size and DPI fix the pixels. If a form gives only a KB limit, leave the dimensions empty — the tool then chooses the clearest pixel size for that KB, which is usually better than guessing a cm size.

Other Sizes and Tools

Need a different limit? Each page opens the same tool with that size already selected.

Frequently Asked Questions