RAM Latency and Bandwidth Calculator

RAM speed (MT/s) and CAS latency (CL) pull in opposite directions: faster memory has higher CL numbers, so the CL alone says little. This calculator converts timings into nanoseconds — the time the memory really takes to answer — and works out the peak bandwidth for your number of channels, so you can compare a DDR4-3600 CL16 kit with DDR5-6000 CL30 on equal terms. A table lists common kits.

How to use this tool

1. Enter the data rate from the kit name (DDR5-6000 → 6000 MT/s).
2. Enter the CAS latency and, if you know them, tRCD, tRP and tRAS (e.g. 30-36-36-76).
3. Choose how many memory channels your platform uses.
4. Compare the nanosecond latency and bandwidth with the table.

Formula

latency (ns) = CL × 2000 ÷ MT/s · clock (MHz) = MT/s ÷ 2 · bandwidth (GB/s) = MT/s × 8 bytes × channels ÷ 1000

DDR memory transfers data twice per clock, so one clock cycle lasts 2000 ÷ MT/s nanoseconds and every timing in cycles converts the same way. Each channel is 64 bits (8 bytes) wide. Sellers often write "6000 MHz" when they mean 6000 MT/s.

Example

DDR4-3200 CL16 answers in 16 × 2000 ÷ 3200 = 10 ns, and so does DDR5-6000 CL30 (30 × 2000 ÷ 6000 = 10 ns) — the same latency — but in dual channel the DDR5 kit moves 6000 × 8 × 2 ÷ 1000 = 96 GB/s against 51.2 GB/s. Its tRCD of 36 cycles is 12 ns.