File Transfer Time Calculator
Estimate upload or download time from file size, connection speed, and overhead
File Transfer Time Calculator — what it does
Enter a file size, a connection speed and a protocol overhead percentage, and get a realistic estimate of how long the transfer will take alongside the effective throughput. It also handles the unit conversion people trip over constantly: connection speeds are quoted in bits per second, file sizes in bytes, and the factor of eight between them breaks most mental estimates.
When this tool helps
- Estimating how long a backup will take to reach cloud storage before starting it at 5 pm.
- Judging whether sending a video project over the office line beats couriering a drive.
- Setting expectations for a client downloading a large deliverable on their connection.
How to use it
- Enter the file size and its unit.
- Enter the connection speed and its unit.
- Adjust the protocol overhead percentage.
- Read the estimated time and effective speed.
Accuracy, limits, and good practice
- A 100 megabit line moves at most 12.5 megabytes per second before overhead — the bits-to-bytes factor of eight is where most estimates go wrong.
- Real transfers rarely sustain the advertised rate; the far end, Wi-Fi conditions and shared usage all cap actual throughput.
- Around 10 percent overhead is a reasonable default for TCP-based transfers; VPNs and unstable links justify more.
Frequently asked questions
Why does my upload take far longer than this estimate?
Most consumer connections are asymmetric: upload speed is a fraction of download. Enter your actual upload rate for upload jobs.
What is protocol overhead?
The share of raw bandwidth spent on packet headers, acknowledgements, encryption and retransmissions rather than your file's bytes.
Is a physical drive ever faster?
For terabytes over ordinary connections, often yes — computing the transfer time here is exactly how you find the crossover.
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Everything above runs inside this page. File Transfer Time Calculator needs no account, no upload, and no server round trip — close the tab and nothing is left behind.
檔案傳輸時間計算器能做什麼
輸入檔案大小、連線速度與協定損耗百分比，即可得到貼近現實的傳輸時間估計與有效速率。它也處理了人人都會絆倒的單位換算：線路速度以「位元」計、檔案大小以「位元組」計，中間差的那個八倍正是多數心算失準的地方。
什麼時候用得上
- 下午五點開跑備份前，先估它要多久才能上到雲端。
- 判斷影片專案走公司線路傳，還是寄硬碟比較快。
- 為客戶在自家網路下載大型交付檔設定合理預期。
使用步驟
- 輸入檔案大小與單位。
- 輸入連線速度與單位。
- 調整協定損耗百分比。
- 查看估計時間與有效速率。
精確度、限制與實務建議
- 100 Mbps 的線路扣除損耗前最多每秒 12.5 MB——位元對位元組的八倍差，就是估算最常錯的地方。
- 實際傳輸很少跑滿標稱速率；對端、Wi-Fi 品質與共用流量都會壓低實際吞吐。
- TCP 類傳輸取 10% 損耗是合理預設；走 VPN 或不穩定線路可以抓更高。
常見問題
為什麼我的上傳比估計慢得多？
多數家用連線不對稱：上傳速度只有下載的幾分之一。上傳工作請填實際的上傳速率。
什麼是協定損耗？
頻寬中花在封包標頭、確認、加密與重傳、而非檔案內容本身的那部分。
寄實體硬碟會更快嗎？
在一般線路傳 TB 級資料時常常會——用這裡算出傳輸時間，正是找出臨界點的方法。
本站相關工具
以上步驟全部在這個頁面內完成，檔案傳輸時間計算器 不需要註冊、不上傳檔案、也不經過伺服器，關閉分頁後不會留下任何資料。