bandwidth calculator
Quickly size the internet speed you really need—at home or in a small office—based on simultaneous activities and users. Or estimate file transfer time given a link speed. Includes protocol efficiency, overhead, concurrency, and a safety margin.
Interactive bandwidth calculator
Required bandwidth
Download required
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Upload required
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Plan recommendation (rounded up)
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Show assumptions
Estimated transfer time
Time (hh:mm:ss)
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Effective throughput
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Show calculation
Data source and methodology
- IEC 80000-13 — Quantities and units of information science (binary/decimal prefixes). IEC
- IETF RFC 6349 — Framework for TCP Throughput Testing (efficiency considerations). RFC-editor
- ITU-T G.1010 — End-user multimedia QoS categories and bitrates (application ranges). ITU
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The formula explained
Activity-based bandwidth (download or upload):
\[ B_{\text{req}} = \frac{\alpha}{\eta}\; \Big( c \cdot \sum_{i=1}^{N} n_i \, r_i \Big) \]
where \(n_i\) is users on activity \(i\), \(r_i\) its bitrate (Mbps), \(c\) the concurrency (0–1), \(\eta\) protocol efficiency (0–1), and \(\alpha\) the safety margin (1+margin).
File transfer time:
\[ t = \frac{S_{\text{bits}}}{R_{\text{link}} \cdot \eta} \quad,\quad S_{\text{bits}} = S \times \kappa \]
with \(S\) the file size, \(\kappa\) the unit factor (e.g., \(1\text{ GB}=10^9\) bytes), \(R_{\text{link}}\) in bits/s, and \(\eta\) efficiency.
Glossary of variables
- Concurrency — Share of users active at once (e.g., 0.4 = 40%).
- Safety margin — Headroom to absorb peaks; \(\alpha = 1 + \text{margin}\).
- Protocol efficiency — Payload fraction after overhead, \(\eta\).
- Bitrate (ri) — Mbps per activity (down/up).
- Required bandwidth — Minimum Mbps to avoid congestion under assumptions.
- Effective throughput — \(R_{\text{link}}\cdot \eta\) accounting for overhead.
How it works: a step-by-step example
Scenario. 2× 4K streaming (25/5 Mbps), 2× HD video call (2.5/2.5), 1× gaming (3/1), concurrency 50%, efficiency 85%, margin 20%.
- Sum raw demand (down): \(2\cdot25 + 2\cdot2.5 + 1\cdot3 = 58\) Mbps.
- Apply concurrency: \(58 \times 0.5 = 29\) Mbps.
- Apply safety: \(\alpha=1.2 \Rightarrow 29 \times 1.2 = 34.8\) Mbps.
- Account for efficiency: \(34.8 / 0.85 \approx 40.9\) Mbps down. Do the same for upload.
- Round up to plan tiers (e.g., 100/20 Mbps) to guarantee headroom.
Frequently asked questions
What activity bitrates should I use?
Use vendor guidance when available. As a rule of thumb: SD stream 3 Mbps, HD 5 Mbps, 4K 25 Mbps; video call SD 1–1.5, HD 2–3; gaming 3–6; web 1; music 0.3–0.6. Adjust if quality/resolution differs.
Decimal vs binary units?
GB (decimal) uses 109 bytes; GiB (binary) uses 230 bytes. For network links, decimal is common; for filesystems, binary is frequent (IEC 80000-13).
Why do tests show lower speed than my plan?
Wi-Fi conditions, ISP shaping, shared backhaul, server caps, and protocol overhead reduce measured throughput vs the advertised tier.
Is latency/jitter considered?
No, this calculator focuses on throughput. Real-time apps may need QoS and low latency; check your router/ISP features.
How big should my safety margin be?
Homes: 15–30%. Small offices or content creators: 25–50%+. Increase if many 4K streams or cloud syncs occur together.
Does upload speed affect cloud backups?
Yes—large backups are upload-bound. Use the File transfer tool with your upstream tier and efficiency.
Can I use this for CCTV sizing?
Yes—treat each camera’s average bitrate as an activity and sum them. For precise CCTV engineering, add motion profiles and VBR headroom.
Tool developed by Ugo Candido. Content reviewed by the CalcDomain Editorial Board.
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