Estimate how long it takes to move files over different USB connections.
MB
GB
TB
USB 1.1 (12 Mbps)
USB 2.0 (High Speed – 480 Mbps)
USB 3.0 / 3.1 Gen 1 (5 Gbps)
USB 3.1 Gen 2 / 3.2 Gen 2 (10 Gbps)
USB 3.2 Gen 2×2 (20 Gbps)
USB 4 / Thunderbolt 3/4 (40 Gbps)
USB 4 v2 (80 Gbps)
Custom Speed (MB/s)
Theoretical Max Speed (100%)
Optimistic Real World (80%)
Typical Real World (60%)
Slow / Many Small Files (40%)
Total Data:–
Effective Speed:–
Estimated Time:–
Understanding USB Transfer Rates
Whether you are backing up a computer, transferring 4K video footage to an external SSD, or moving photos from a camera, knowing how long a transfer will take is essential for workflow management. This calculator helps you estimate transfer times based on file size and the USB generation you are using.
Why Theoretical Speed ≠ Real Speed
You may notice that your file transfers rarely reach the maximum speed advertised on the box. This is due to several factors:
Protocol Overhead: USB communication requires command and control data, not just your files. Techniques like 8b/10b or 128b/132b encoding use a portion of the bandwidth for signaling.
Hardware Limitations: A USB 3.0 port supports 5 Gbps, but if you plug in a slow mechanical hard drive that can only write at 100 MB/s, the drive becomes the bottleneck, not the USB port.
File Type: Transferring one massive 10GB file is much faster than transferring 10,000 small 1MB files. Small files require constant opening, closing, and updating of the file system table, which slows down the process significantly.
Pro Tip: When moving thousands of small files, zip them into a single archive first. This allows the transfer to utilize the maximum sequential read/write speed of your drive.
USB Generations Explained
The USB naming scheme has changed several times, leading to confusion. Here is a quick breakdown used in our calculations:
USB 2.0: The old standard. Max theoretical speed is 480 Mbps (~60 MB/s), but real-world usually tops out around 30-40 MB/s.
USB 3.2 Gen 1 (formerly USB 3.0): The standard blue port. Offers 5 Gbps (~625 MB/s). Real-world speeds often sit between 300-450 MB/s depending on the drive.
USB 3.2 Gen 2: Often found on newer laptops and SSDs. Offers 10 Gbps (~1,250 MB/s).
USB 4 / Thunderbolt: The latest standard utilizing USB-C connectors, offering speeds up to 40 Gbps (~5,000 MB/s).
Bits vs. Bytes
It is important to distinguish between Megabits (Mb) and Megabytes (MB). USB speeds are usually rated in bits (e.g., 480 Mbps), while file sizes are measured in bytes (e.g., 500 MB). Since 1 Byte equals 8 bits, you must divide the advertised speed by 8 to get the theoretical maximum in MB/s.
// Toggle custom speed input visibility
document.getElementById('usbStandard').onclick = function() {
var val = this.value;
var customGroup = document.getElementById('customSpeedGroup');
if (val === 'custom') {
customGroup.style.display = 'block';
} else {
customGroup.style.display = 'none';
}
};
function calculateTransferTime() {
var sizeInput = parseFloat(document.getElementById('dataSize').value);
var unit = document.getElementById('dataUnit').value;
var standardSelect = document.getElementById('usbStandard');
var standardVal = standardSelect.value;
var efficiency = parseFloat(document.getElementById('efficiency').value);
// Basic Validation
if (isNaN(sizeInput) || sizeInput <= 0) {
alert("Please enter a valid positive number for the data size.");
return;
}
// Determine Speed in MB/s
var speedMBps = 0;
if (standardVal === 'custom') {
speedMBps = parseFloat(document.getElementById('customSpeed').value);
if (isNaN(speedMBps) || speedMBps <= 0) {
alert("Please enter a valid custom speed.");
return;
}
} else {
speedMBps = parseFloat(standardVal);
}
// Apply Efficiency
// speedMBps derived from dropdown is the theoretical MAX in MB/s (e.g. 5Gbps / 8 = 625)
var realSpeed = speedMBps * efficiency;
// Convert File Size to MB for calculation
// Using decimal standard (1000) common for data transfer rates, though OS uses 1024.
// We will use 1000 to match Gbps/Mbps metric logic, or 1024 if preferred.
// Let's use 1024 (Binary) as that is what users see in Windows properties.
var sizeInMB = 0;
if (unit === 'MB') {
sizeInMB = sizeInput;
} else if (unit === 'GB') {
sizeInMB = sizeInput * 1024;
} else if (unit === 'TB') {
sizeInMB = sizeInput * 1024 * 1024;
}
// Calculate Time in Seconds
// Time = Data / Speed
var totalSeconds = sizeInMB / realSpeed;
// Formatting Output
var formattedTime = formatTime(totalSeconds);
var formattedSpeed = realSpeed.toFixed(1) + " MB/s";
// Format Total Data display
var formattedData = sizeInput + " " + unit;
// Display Results
document.getElementById('resTotalData').innerHTML = formattedData;
document.getElementById('resSpeed').innerHTML = formattedSpeed;
document.getElementById('resTime').innerHTML = formattedTime;
document.getElementById('resultsArea').style.display = 'block';
}
function formatTime(seconds) {
if (seconds === Infinity || isNaN(seconds)) return "Unknown";
if (seconds 0 ? d + (d == 1 ? " day, " : " days, ") : "";
var hDisplay = h > 0 ? h + (h == 1 ? " hour, " : " hours, ") : "";
var mDisplay = m > 0 ? m + (m == 1 ? " min, " : " mins, ") : "";
var sDisplay = s > 0 ? s + (s == 1 ? " sec" : " secs") : "";
// Cleanup trailing commas if needed, but the logic above adds spaces
// Let's return only the two largest units if it's very long, or all for precision
// For simplicity, showing all non-zero units
var result = dDisplay + hDisplay + mDisplay + sDisplay;
// Remove trailing comma/space if present
if (result.endsWith(", ")) {
result = result.substring(0, result.length – 2);
}
// Fallback for very short time appearing empty due to logic
if (result === "") return Math.round(seconds * 100) / 100 + " seconds";
return result;
}