PoE Switch Power Budget Calculator

Assumptions

• All endpoints are assumed to draw the entered maximum power at the same time.

Important notes

• Check each port separately for PSE class, per-port power limits, cable length and endpoint startup peaks. The aggregate budget does not establish per-port compatibility.

Standards and sources

• IEEE 802.3 Ethernet Working Group

Verified: 2026-09-05

Calculation method

Endpoint power = count × power per device (W). Required budget = endpoint power × (1 + cable loss % / 100) × (1 + reserve % / 100). Remaining budget = switch PoE budget − required budget.

Worked example

Planning example: 24 endpoints at 12 W each, 10% cable loss, 20% reserve and a 400 W switch budget. Endpoint power is 288 W; required budget is 380.16 W; remaining budget is 19.84 W. The two allowances are multiplied, not simply added.

Scope and limitations

This checks aggregate power only. Verify PSE/PD class, per-port limits, cabling and startup peaks separately. This is an illustrative calculation, not a device measurement or customer project result.