Add Bytes Calculator: How to Sum File Sizes

This calculator adds together file sizes in bytes, kilobytes, megabytes, gigabytes, and other units, returning the total in bytes and in larger units. You enter each size as a number and choose its unit; the calculator converts everything to bytes, sums them, and shows the result in bytes, kilobytes, megabytes, and gigabytes. It is useful for estimating storage needs, comparing download quotas, or simply checking how much space a group of files will occupy.

Formula

The core formula is simple: Total bytes = Sizeâ‚� + Sizeâ‚‚ + … + Sizeâ‚™, where each size is expressed in bytes. To convert a size given in a different unit to bytes, multiply by the appropriate power of 1024:

• 1 kilobyte (KB) = 1024 bytes
• 1 megabyte (MB) = 1024 KB = 1,048,576 bytes
• 1 gigabyte (GB) = 1024 MB = 1,073,741,824 bytes
• 1 terabyte (TB) = 1024 GB = 1,099,511,627,776 bytes

After summing, you can convert back to larger units by dividing the total bytes by 1024, 1024², or 1024³ as needed. The calculator uses the binary (base-2) definition, which is the standard in most operating systems and file managers.

Worked Example

Using the default values: Size 1 = 1,048,576 bytes (1 MB), Size 2 = 5,242,880 bytes (5 MB), Size 3 = 10,485,760 bytes (10 MB).

1. Total bytes = 1,048,576 + 5,242,880 + 10,485,760 = 16,777,216 bytes
2. Total KB = 16,777,216 ÷ 1024 = 16,384 KB
3. Total MB = 16,777,216 ÷ 1,048,576 = 16 MB
4. Total GB = 16,777,216 ÷ 1,073,741,824 = 0.0156 GB

The calculator displays the same results: 16,777,216 bytes, 16,384 KB, 16 MB, and 0.0156 GB.

Why Use 1024 Instead of 1000?

Computers store data in binary, and 2¹� = 1024 is a natural grouping. Most operating systems, file managers, and memory specifications use 1024 for KB, MB, GB, etc. However, hard drive manufacturers and some network speeds use decimal units (1 KB = 1000 bytes) to make capacities appear larger. This discrepancy can lead to confusion: a 500 GB hard drive shows as 465 GB in Windows because the OS uses binary. When adding file sizes, always know which convention your source uses. This calculator follows the binary convention, which is what you see in most file properties.

Common Mistakes and How to Avoid Them

• Mixing units without conversion: Adding 1 MB and 500 KB as 1 + 500 gives 501, but the correct total is 1.488 MB (or 1524 KB). Always convert to bytes first.
• Confusing MB and MiB: Some tools use MiB (mebibyte) to mean 1024² bytes, while MB can mean 1000² or 1024². This calculator uses MB as 1024² bytes, matching common usage in Windows and macOS.
• Rounding too early: If you round each size to two decimals before adding, the total can be off by several bytes. Keep full precision until the final answer.
• Forgetting to include all files: When estimating a folder, remember hidden files and subfolders. Use the calculator for a quick sum, but for exact totals, rely on your OS’s properties dialog.

When to Use This Calculator

Use it when you need to:

• Estimate total storage for a batch of files before downloading or copying.
• Check if a set of files fits on a USB drive, SD card, or cloud storage plan.
• Compare the total size of multiple folders or backups.
• Plan data transfer time (divide total bytes by your transfer rate).

For example, if you have 30 photos of 3 MB each, the total is 90 MB, which fits easily on a 1 GB drive. But if you have 500 photos of 5 MB each, that’s 2.5 GB, which may exceed a free cloud storage tier.

Limitations and Alternatives

This calculator only sums sizes you enter manually. It cannot scan a folder or read file properties. For that, use your operating system’s file manager (right-click → Properties on Windows, Get Info on macOS) or a disk usage analyzer. Also, the calculator assumes binary units; if you work with decimal-based storage (e.g., network speeds in Mbps), convert accordingly. For very large numbers (terabytes and beyond), the calculator still works but may show many decimal places; consider using scientific notation or converting to TB.

Frequently Asked Questions

How do I convert bytes to megabytes?

Divide the number of bytes by 1,048,576 (1024²). For example, 5,242,880 bytes ÷ 1,048,576 = 5 MB. If you want decimal MB (1,000,000 bytes), divide by 1,000,000 instead, but note that most OSes use binary.

Why does my 1 TB drive show only 931 GB?

Because drive manufacturers use decimal units (1 TB = 1,000,000,000,000 bytes) while operating systems use binary (1 TB = 1,099,511,627,776 bytes). The difference is about 10%. This is normal and not a defect.

Can I add sizes with different units in one calculation?

Yes, but you must convert them all to the same unit first. This calculator does that automatically when you enter each size with its unit. If you do it manually, always convert to bytes before adding.

What is the difference between KB and KiB?

KB (kilobyte) can mean 1000 or 1024 bytes, while KiB (kibibyte) always means 1024 bytes. The binary prefixes (Ki, Mi, Gi) were introduced to end confusion, but many systems still use KB/MB/GB with binary meaning. This calculator uses KB = 1024 bytes.

Does this calculator work for network speeds?

No, network speeds are usually measured in bits per second (bps), not bytes. To convert bytes to bits, multiply by 8. For example, a 10 MB file is 80 megabits. This calculator only sums file sizes, not transfer rates.

Related

• Aperture and Shutter Speed Calculator: Find Exposure
• APS-C Crop Factor Calculator: Sensor Size and FOV
• 65 Inch TV Mounting Height Calculator and Guide

in a | Size 1 | bytes | 1048576 | 0
in b | Size 2 | bytes | 5242880 | 0
in c | Size 3 | bytes | 10485760 | 0
out total_bytes | Total bytes | bytes | a + b + c | 0
out total_kb | Total kilobytes | KB | (a + b + c) / 1024 | 2
out total_mb | Total megabytes | MB | (a + b + c) / (1024 * 1024) | 2
out total_gb | Total gigabytes | GB | (a + b + c) / (1024 * 1024 * 1024) | 4