Router & Ethernet Speed Bottleneck Calculator

Find whether a 100Mbps or 1Gbps port is holding back your broadband package.

Router and Ethernet diagnosis

Identify the Port Limiting Your Broadband Speed

Choose your advertised download speed and the link rates of your equipment. Estimate the single-device wired interface ceiling from WAN, LAN and Ethernet link rates before buying hardware. This is a theoretical port-limit calculation, not a live router-speed test.

Ethernet link-rate limits

Find the slowest link in your setup

Run Broadband Speed Test

Live network path

Estimated speed at each junction

Updates as you change settings
  1. 01 · IncomingBroadband package
    —Mbps · upper limitAdvertised download
  2. 02 · Router entryRouter WAN port
    —Mbps · upper limitAfter internet port
  3. 03 · Local linkRouter LAN port
    —Mbps · upper limitAfter LAN or switch port
  4. 04 · DestinationDevice Ethernet port
    —Mbps · upper limitAt this device

These figures are estimated throughput ceilings, not guaranteed or measured internet speeds. Enter your equipment link rates above.

Approximate single-device download ceiling

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What to check next

    Why speeds stop short

    Common 100Mbps, gigabit and multi-gigabit limits

    100Mbps when you pay for 500Mbps?

    A port or Ethernet link negotiated at Fast Ethernet (100Mbps) commonly limits real throughput to roughly 94Mbps. Check the device link rate, router ports and cable terminations. A Cat5e cable is not inherently limited to 100Mbps; it can support gigabit and, in suitable conditions, faster links.

    About 940Mbps on 1Gb Ethernet?

    This can be normal for a good gigabit Ethernet link because protocols use part of the nominal rate. A 2Gbps package may need 2.5GbE-capable ports at both ends, and perhaps a multi-gig switch or adapter, before one device can exceed gigabit speeds.

    What about Wi-Fi 6 and Wi-Fi 7?

    Advertised Wi-Fi connection rates are not real download throughput. Signal quality, channel width, antenna count, device hardware, interference and network load matter. A Wi-Fi bottleneck is best confirmed by comparing the same device using a wired connection.

    When faster hardware is not the answer

    If every wired link has sufficient capacity but the measured internet speed is still low, look at background traffic, router processing capacity, provider provisioning, line faults and test-server limitations before buying equipment.

    This calculator estimates the speed ceiling imposed by WAN, LAN and device Ethernet link rates; it does not measure your router CPU, wireless signal or ISP line. For a broader diagnosis before replacing hardware, see do I need a new router?

    Choose hardware only after checking the limitation

    If a device port really is limited, compare Ethernet adapters and switches that match your router, cable run and package speed. For Wi-Fi issues, begin with coverage and placement rather than an automatic upgrade.

    Compare Home RoutersRouter hardware guidance and eligible Amazon purchasing links.Test Wi-Fi Room SpeedsDiscover whether the slowdown is location-specific.

    Affiliate disclosure: LinkSpeed may earn a commission from qualifying purchases through affiliate links on product guides.

    Bottleneck calculator questions

    Why does this use 94% for Ethernet?

    It is a rough allowance for protocol overhead that produces useful ballpark ceilings such as 94Mbps and 940Mbps. Actual usable throughput varies with Ethernet framing, IP, transport, PPPoE, VPNs, device processing and test conditions.

    Does a 2.5Gbps WAN port guarantee 2.5Gbps Wi-Fi?

    No. It only removes one potential wired-port cap. Real Wi-Fi throughput varies substantially and is not guaranteed by the router's port specification.

    How do I check my true Ethernet link rate?

    Windows, macOS and many router dashboards show the currently negotiated Ethernet link speed. A port rated for 1Gbps can negotiate at 100Mbps when a cable or connector has a fault.