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Calcimator

Data Center Bandwidth Calculator

Calculate network bandwidth, switch counts, and uplink capacity from server count and connectivity requirements.

Inputs

%
%

Results

Total access bandwidth (Gbps)

2,000

Aggregation bandwidth (Gbps)666.67
WAN uplink needed (Gbps)66.67
ToR switches needed5
Spine switches needed2
Bisectional bandwidth (Gbps)200
Monthly transfer (TB)194,400
Total server ports200
How to Use This Calculator
  1. Enter the number of servers and average bandwidth per server in Mbps.
  2. Set oversubscription ratio and external uplink speed.
  3. Review total internal bandwidth requirement and uplink utilization.
  4. Verify uplink capacity provides adequate headroom for peak traffic bursts.
  5. Use the output to size core switches, distribution switches, and WAN circuits.

How the result changes with Number of servers

Number of serversTotal access bandwidth (Gbps)
10,001200,020
35,001700,020
65,0001,300,000
90,0001,800,000

What each input means

Number of servers
Total physical or virtual servers requiring network connectivity.
Port speed (Gbps)
Network port speed per connection. Common: 1, 10, 25, 100 Gbps.
NICs per server
Network interfaces per server (2 for redundancy, 4 for bonded).
Oversubscription ratio
Aggregation oversubscription (3 = 3:1). Lower = more bandwidth. 1:1 = non-blocking.
Avg utilization (%)
Average network utilization across all ports.
WAN bandwidth (%)
Percentage of aggregation bandwidth needed for WAN/internet uplinks.

What each result means

Total access bandwidth (Gbps)
Sum of all server-facing port bandwidth.
Aggregation bandwidth (Gbps)
Bandwidth at aggregation layer after oversubscription.
WAN uplink needed (Gbps)
Internet/WAN uplink bandwidth required.
ToR switches needed
Top-of-Rack leaf switches (48 server ports each).
Spine switches needed
Spine-layer switches (32 ports each, minimum 2 for redundancy).
Bisectional bandwidth (Gbps)
Total spine-leaf bisectional bandwidth.
Monthly transfer (TB)
Estimated monthly data transfer at average utilization.
Total server ports
Total NIC ports across all servers.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Number of servers = 100, Port speed (Gbps) = 10, NICs per server = 2, Oversubscription ratio = 3 = 6 input(s) provided
  2. Calculate Total access bandwidth
    Total access bandwidth = serverCount * portSpeedGbps * nicsPerServer
    2000 = 2000
  3. Calculate Aggregation bandwidth
    Aggregation bandwidth = totalAccessBandwidthGbps / oversubRatio
    666.67 = 666.67
  4. Calculate WAN uplink needed
    WAN uplink needed = aggregationBandwidthGbps * (wanPct / 100)
    66.67 = 66.67

Engine last updated .

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