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DDR timing utility

DDR Memory Latency Calculator

Convert a DDR data rate in MT/s and CAS latency in clock cycles into the time represented by that CAS timing in nanoseconds. The result isolates CL/tCL timing; it is not complete memory, CPU, or application latency.

Interactive calculation

Enter the DDR data rate and CL

Enter the effective DDR data rate in MT/s and the CAS latency value in whole clock cycles. The 6000 MT/s CL30 defaults are only a calculation example, not a recommendation or an “ideal RAM” claim.

MT/s is a transfer rate, not the underlying clock. Double Data Rate memory transfers on both clock edges, so a 6000 MT/s data rate corresponds to a 3000 MHz memory clock for this timing conversion.

CL is entered as whole clock cycles. This tool converts that one timing into time; it does not infer the rest of the RAM timing set.

CAS timing at 6,000 MT/s · CL30

10.00 ns

Time represented by the entered CAS-latency cycles—not total DRAM, memory-controller, or system latency.

Underlying memory clock
3,000 MHz
Clock-period duration
0.333 ns
Equivalent formula
2000 × 30 ÷ 6,000

Why the factor 2000 appears: DDR data rate is twice the memory clock, and one MHz cycle lasts 1000/MHz nanoseconds. Substituting MT/s ÷ 2 for the clock gives 2000 ÷ MT/s nanoseconds per memory clock cycle.

What this does not measure: row activation/precharge delays, other timings, memory-controller scheduling, topology, cache behavior, workload access patterns, bandwidth, FPS, or complete application responsiveness.

Clock relationship

Why MT/s is not the memory clock

DDR means Double Data Rate: data transfers occur at twice the underlying memory-clock frequency. A 6000 MT/s data rate therefore corresponds to a 3000 MHz memory clock for this timing conversion.

A 3000 MHz clock period is about 0.333 ns. CL30 represents 30 of those clock cycles, so the CAS timing is about 10 ns.

Algebraically, the same relationship is CAS ns = 2000 × CL ÷ MT/s. The factor 2000 comes from converting MHz cycles to nanoseconds and dividing the DDR data rate by two to recover the underlying clock.

Interpretation

CAS timing is one delay, not total RAM latency

CAS latency is expressed in clock cycles and represents the delay associated with the read/CAS timing before data becomes available. Converting CL to nanoseconds makes timing values at different DDR data rates easier to compare on the same time scale.

A complete memory access can involve other timings such as row-to-column and precharge delays, plus memory-controller scheduling, rank/channel topology, access pattern, caches, and platform behavior.

This calculator therefore does not predict bandwidth, game FPS, CPU performance, full random-access latency, or application responsiveness from CL alone.

References

Memory timing and clock guidance

These current manufacturer references support the CL-cycle definition, DDR clock/data-rate relationship, and MT/s-to-nanoseconds calculation. They do not provide a benchmark or ranking for RAM kits.

  1. 01 · Kingston Technology

    CAS latency, clock cycles, and MT/s-to-nanoseconds formula

  2. 02 · Kingston Technology

    DDR data rate is twice the memory bus frequency

  3. 03 · Micron

    DDR5 part catalog with paired MHz, MT/s, and CAS-latency fields

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