Datacenter Math
Three small calculators that follow a rack from the grid to the price of a token: rack power and line current, KV cache concurrency, and dollars per million tokens. The formulas and default numbers come from the From Watts to Tokens course. Every number names its denominator. Back to rahilbhavan.com.
Rack to grid
- Rack IT power
- kW per rack
- Line current, AC three-phase
- A per line
- Conductor current, DC
- A per conductor
- Facility power
- MW at the meter
- Facility energy
- MWh per day
- Water intake
- L per day
Source: From Watts to Tokens, draft updated 2026-09-10. 100 kW at 480 V AC draws about 120 A per line; at 800 V DC, 125 A per conductor. 100 MWh IT per day at 1.25 L/kWh is 125,000 L per day.
KV cache and concurrency
- KV cache size
- KiB per token
- Resident requests
- full-context requests in the pool
Source: From Watts to Tokens, draft updated 2026-09-10. Llama 3.1 70B in BF16 is 320 KiB per token; a 64 GiB pool holds 25 requests at 8K context and 6 at 32K. Excludes prefix sharing, block rounding and weights.
$/token
- Token cost
- $ per million tokens
Source: From Watts to Tokens, draft updated 2026-09-10. Rental ranges are 25th to 75th percentile one-year terms per GPU-hour, dated as labelled. Compute cost only; excludes occupancy, networking and margin.