100G to 400G Upgrade Calculator
Consolidate 100G ports into 400G: port count saved, capacity delivered and power per gigabit improvement.
About 100G to 400G Upgrade Calculator
A 400G port carries four 100G lanes, so four existing links collapse onto one port and one trunk. Because a 400G optic draws roughly 12 W against 4.5 W for 100G, the per-gigabit power falls by about a third even though each module draws more. Switch port count and optical power are the two limits in a modern spine rack, and 400G consolidation relieves both without new fibre if MPO-16 trunks are already in place.
Formula
100G to 400G Upgrade
400G ports = ceil(100G ports ÷ 4) when each 400G port breaks out to 4 × 100G; power per gigabit = 400G optic power ÷ 400.
- breakout
- 400G port split into 4 × 100G, 8 × 50G or 2 × 200G lanes
- power per gigabit
- Optical watts divided by delivered capacity — the figure that scales in a rack
Worked example
With the default values below, 100G to 400G Upgrade Calculator returns 400G Ports Required of 32. Change any input above and every figure here is recalculated in your browser.
Inputs used
- 100G ports in serviceaccepts 1–20,000 ports
- 128 ports
- 400G breakout modeone of 4 × 100G, 8 × 50G, 2 × 200G
- 4 × 100G
- Power per 100G opticaccepts 0.5–30 W
- 4.5 W
- Power per 400G opticaccepts 1–60 W
- 12 W
Results
- 400G Ports Required
- 32 ports
- Capacity Delivered
- 12,800 Gbps
- Switch Ports Freed
- 96 ports
- Optical Power Saved
- 192.0 W
- Power per Gigabit after Upgrade
- 0.0300 W/Gbps
- Logical Ports after Breakout
- 128 ports
Step by step
- 1Values used
- 2100G to 400G Upgrade
- 3400G Ports Required= 32 ports
- 4Capacity Delivered= 12,800 Gbps
- 5Switch Ports Freed= 96 ports
- 6Optical Power Saved= 192.0 W
- 7Power per Gigabit after Upgrade= 0.0300 W/Gbps
- 8Logical Ports after Breakout= 128 ports
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is 100G to 400G Upgrade calculated?
400G ports = ceil(100G ports ÷ 4) when each 400G port breaks out to 4 × 100G; power per gigabit = 400G optic power ÷ 400. A 400G port carries four 100G lanes, so four existing links collapse onto one port and one trunk. Because a 400G optic draws roughly 12 W against 4.5 W for 100G, the per-gigabit power falls by about a third even though each module draws more.
Why does 100G to 400G Upgrade matter?
Switch port count and optical power are the two limits in a modern spine rack, and 400G consolidation relieves both without new fibre if MPO-16 trunks are already in place.
What values do I need to enter?
This calculator takes 4 inputs: 100G ports in service, 400G breakout mode, Power per 100G optic, Power per 400G optic. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.