Resize and compress photos for online forms.
Set the pixel dimensions and maximum file size you need. Free, with no photo uploads. SizeKit also has everyday calculators and converters, with guides that explain every result.
Make it yours
Your photo
A little smaller. A lot simpler.
Drop a photo here to get started.
Calculators & converters
Eight everyday tools for percentages, discounts, BMI, age and unit conversion. No signup, and nothing you enter leaves your browser.
Percentage Calculator
Find a percentage of a number, work out what percent one number is of another, or find the whole from a part.
Percentage Change Calculator
Work out the percentage increase or decrease between two values, or apply a percentage rise or fall to a number.
Discount Calculator
See the sale price and how much you save, or find the discount percentage from an original and a sale price.
BMI Calculator
Calculate body mass index from height and weight in metric or imperial units. A screening number, not a diagnosis.
Age Calculator
Get an exact age in years, months and days, today or on any date, plus days until the next birthday.
Length Converter
Convert between millimetres, centimetres, metres, kilometres, inches, feet, yards and miles.
Weight Converter
Convert between milligrams, grams, kilograms, tonnes, ounces, pounds and stone.
Height Converter
Convert a height between centimetres and feet and inches, with the exact working shown.
Small tools, explained properly
SizeKit is built for quick, practical jobs. Each tool does one thing, shows how it got the answer and says where the answer can be wrong.
Private by design
The photo resizer and every calculator run in your browser. The photo you choose and the numbers you enter are not uploaded or saved.
Formulas you can check
Every calculator page shows its formula and a worked example, so you can confirm a result by hand instead of taking it on trust.
Honest about limits
BMI is a screening number, not a diagnosis. A resized photo may still be rejected by a strict form. Each page says what the result does and does not mean.
How to resize a photo to a KB limit
Pick a photo
From your phone or computer.
Your file never leaves your device.
Set your limits
Enter your limit, such as 100 KB, and any required width and height in pixels.
Save and go
Preview your result and download.
No signup or watermark.
A smaller photo, ready for your form
Our built-in sample started at 233.2 KB and 1600 × 1067 pixels. With an 800-pixel width, proportions locked and a 100 KB limit, the JPG result was 94.0 KB at 800 × 534 pixels.
Your result depends on the image and browser. Always preview the downloaded photo before submitting it.
1600 × 1067 px → 800 × 534 px
Below the 100 KB limitPhoto resizing questions
Check your form’s own instructions for its accepted format, dimensions and file-size range.
What is the difference between KB and pixels?
Pixels describe your photo’s width and height. KB describes how much storage the file uses. Two photos with the same dimensions can have different file sizes. SizeKit lets you set both the dimensions and a maximum KB limit.
How do I compress a photo to 100 KB?
Choose a JPG, PNG or WebP photo, select 100 KB, and enter any dimensions your form requires. Keep proportions on to preserve the original shape. Select JPG or WebP, click Resize & compress, then preview and download the result.
Will my photo be exactly 100 KB?
No. The setting is a maximum, not an exact size or a minimum. A smaller result is normal. SizeKit uses 1 KB = 1,000 bytes. If your form specifies a minimum as well as a maximum, check that the downloaded file meets both.
Does compression reduce image quality?
It can. SizeKit adjusts JPG or WebP quality to meet your limit while keeping your chosen dimensions. Very small limits can blur fine details. Use the largest file size your form allows, and check faces, text and signature strokes before submitting.
What if the image cannot fit under my limit?
SizeKit shows an error instead of silently changing your chosen dimensions. If the form allows it, reduce the width and height or increase the KB limit. If both requirements are fixed, try a less detailed image or crop it in a photo editor first.
How do I avoid stretching my photo?
Leave Keep proportions on and change one dimension. If your form requires a different shape, crop the photo in a photo editor before resizing it here. Turning proportions off lets you set both dimensions independently, but may stretch the image. SizeKit does not crop photos.
Are my photos uploaded or stored?
Photo resizing and compression happen in your browser. SizeKit does not send the photo you select to a server or store it in an online account. Download your result before closing or reloading the page.
Which file formats can I use?
Choose a JPG, PNG or WebP image up to 20 MB and 40 megapixels. Download as JPG or WebP, with output dimensions from 1 to 4096 pixels per side. JPG fills transparent areas with white; WebP can preserve transparency. PNG output, HEIC and PDF are not supported. Animated WebP exports as a still image.
Get your photo accepted, without the guesswork
Compress a photo to 100 KB
Set the limit, check the result and solve common upload errors.
KB versus pixels
Understand two separate requirements before changing your photo.
JPG or WebP?
Choose a format your destination accepts and handle transparency.
US visa photo size
600 × 600 pixels, 240 KB and the rules behind them.
Pakistan passport photo
What the official page asks for, and why not to crop it.
Reduce to 50 KB or 20 KB
Why tiny limits are hard and how to reach them.
Understand the numbers, not just the answer
Plain-English guides that go with the calculators, from percentages and discounts to BMI, age and unit conversion.
How to calculate percentages
The three questions behind almost every percentage problem, with worked examples and shortcuts you can do in your head.
Percentage change explained
How to calculate an increase or decrease, why +50% then −50% does not get you back, and percent versus percentage points.
How discounts and sale prices work
Working out sale prices, finding the real discount from two prices, and why stacked discounts do not simply add up.
How BMI is calculated and what it can and cannot tell you
The formula, the adult categories, and the honest limits of a number built from only height and weight.
How age is calculated in years, months and days
Why counting birthdays is simple but counting months is not, and how leap days and end-of-month dates are handled.
Unit conversion basics
How conversion factors work, which ones are exact, and the mistakes that cause most wrong answers.
SizeKit reduces image quality to meet your limit while keeping your chosen dimensions. If the limit is too small, we’ll ask you to adjust it. Use WebP to preserve transparency. Animated images export as a still frame.