ddr5 timing calculator

What this DDR5 timing calculator does

DDR5 kits are usually advertised with two big numbers: speed (for example, DDR5-6000) and CAS latency (such as CL30). But those numbers are not in the same unit. Speed is in mega-transfers per second (MT/s), while timings are measured in clock cycles. This calculator converts those cycle values into real-world nanoseconds so you can compare memory kits more accurately.

In practical terms, this helps you answer questions like:

• Is DDR5-6400 CL32 actually faster in latency than DDR5-6000 CL30?
• How much delay comes from tRCD and tRP in addition to CAS?
• What bandwidth increase do I get from higher transfer rates and more channels?

How the math works

1) Clock period in nanoseconds

DDR memory transfers data on both clock edges, so the internal clock is half the MT/s value:

• Memory Clock (MHz) = MT/s ÷ 2
• Clock Period (ns) = 2000 ÷ MT/s

Example: DDR5-6000 has a clock period of 2000/6000 = 0.333 ns per cycle.

2) Timing conversion

To convert any timing from cycles to nanoseconds, multiply by the clock period:

• Latency (ns) = Timing (cycles) × Clock Period (ns)

So CL30 at DDR5-6000 is about 10.00 ns.

3) Useful combined timings

• Closed-page read estimate: tRCD + tCL
• Row cycle (tRC): tRAS + tRP

These combinations are useful because real workloads often trigger more than just CAS delay.

4) Theoretical bandwidth

Bandwidth depends on transfer rate, bus width, and channels:

• GB/s = (MT/s × (Bus Width ÷ 8) × Channels) ÷ 1000

This is a peak theoretical value. Real application throughput will be lower due to protocol overhead, controller behavior, and access patterns.

How to use the results

Latency-focused workloads

Competitive games, certain simulation engines, and responsive desktop use can benefit from lower first-word latency. If two kits have similar bandwidth, the one with lower nanosecond latency may feel snappier.

Bandwidth-focused workloads

Rendering, scientific workloads, compression, and integrated GPU scenarios often scale with throughput. In those cases, faster MT/s and more channels can outweigh a small latency penalty.

Balance matters

Best overall tuning usually comes from balancing both:

• Raise memory data rate in stable steps.
• Tighten timings where possible (especially tCL, tRCD, and tRP).
• Validate using long stability tests, not just a quick benchmark run.

Practical DDR5 tuning tips

• Start from a known-good profile: XMP or EXPO settings are useful baselines.
• Change one variable at a time: speed first, then primaries, then secondaries.
• Watch memory controller limits: CPU IMC quality varies significantly.
• Account for motherboard topology: board layout can affect maximum stable frequency.
• Stability test thoroughly: test overnight before calling a profile daily-stable.

Example comparison

Suppose you are deciding between DDR5-6000 CL30 and DDR5-6400 CL32:

• DDR5-6000 CL30 → CAS latency ≈ 10.00 ns
• DDR5-6400 CL32 → CAS latency ≈ 10.00 ns

CAS latency is effectively tied, but DDR5-6400 provides more peak bandwidth. That means your best choice depends on workload type, platform stability, and price.

Final thoughts

Raw timing numbers can look confusing until everything is converted into the same unit. Use this DDR5 timing calculator to compare kits on equal footing, then validate with real-world benchmarks and stability tests. If you are building a new system, this approach can help you avoid paying extra for settings that provide little practical benefit.