Ethernet PHY Budget Calculator

Calculate cable insertion loss budget for 10/100/1000/2.5G/10G BASE-T Ethernet. Verify cable length + connectors fit within spec.

Calculator Electronics Updated Apr 23, 2026
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How to Use
  1. Pick Ethernet standard (100BASE-T, 1000BASE-T, 2.5GBASE-T, 10GBASE-T).
  2. Enter cable length and category (Cat5e, Cat6, Cat6A, Cat7).
  3. Tool computes total insertion loss and verifies against spec.
Input
m
Presets
Channel Insertion Loss
Cable IL
—dB
Total IL
—dB
Spec Limit
—dB
Verdict
—

Show Work

Enter values.

Reference

Cat5e/6 IL @ 1 Gbps
~20 dB at 100m
100 MHz channel.
Cat6A IL @ 10 Gbps
~35 dB at 100m
500 MHz channel.
Conn IL
~0.4 dB each
RJ45 at 500 MHz.
Max length
100 m all cats
10GBASE-T: 55m Cat6, 100m Cat6A.
10G Spec
~38 dB total
Channel budget.
Scale
IL ∝ √f · length
Skin-effect.

History of BASE-T Ethernet

10BASE-T (1990) ran over 100m of Cat3 UTP at 10 Mbps. 100BASE-TX (1995, Fast Ethernet) required Cat5. 1000BASE-T (1999, Gigabit) packed 250 Mbps x 4 pairs over Cat5e with PAM-5 signaling. 10GBASE-T (2006) pushed Cat6A to the edge of copper bandwidth with complex DSP equalization. Each generation tightened cabling spec: Cat5 (100 MHz), Cat5e (100 MHz, tighter NEXT), Cat6 (250 MHz), Cat6A (500 MHz), Cat8 (2 GHz for 25/40GBASE-T). Beyond Cat8, copper gives way to fiber.

About This Calculator

Pick Ethernet standard, cable category, and length. The tool estimates insertion loss at each standard\'s relevant frequency (100 MHz for 1GBASE-T, 400 MHz for 10GBASE-T) using approximate dB/meter values per cable category, then adds connector loss (0.4 dB each) and compares to the channel-IL spec.

This is a simplified budget — full certification uses NEXT, FEXT, return loss, and PowerSum metrics with a cable tester (Fluke DSX). Everything runs client-side.

Frequently Asked Questions

Why 100m limit?

Copper attenuation at relevant frequencies + PHY DSP can handle up to ~70 dB round-trip insertion loss. 100m of Cat6 gives exactly this at 10GBASE-T frequencies. Above 100m the PHY can\'t train reliably.

Cat6 vs 6A?

Cat6: 250 MHz bandwidth, 55m max at 10GBASE-T (performance-dependent). Cat6A: 500 MHz, full 100m at 10GBASE-T. Cat7: 600 MHz + shielding for EMC.

Patch cables?

Each RJ45 connector adds ~0.4 dB. Patch cords are typically stranded (more loss than solid-core horizontal cable). Spec allows 10m patch at each end + 90m horizontal = 100m total.

Common Use Cases

Office Build-Out

Cat6A 90m horizontal + 5m patch each end = 100m total. 10GBASE-T OK.

Campus Run

120m Cat6A single-run 10GBASE-T: likely fails. Use fiber or two 60m segments.

IoT Short

Cat5e 25m 100BASE-T for security camera: plenty of margin.

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