RAM Latency Calculator

What Is RAM Latency?

RAM latency is the delay between when the memory controller requests data and when the RAM module makes it available, measured in nanoseconds. Lower latency means faster response. CAS latency alone is not enough—you must also account for the memory clock speed or data rate.

DDR RAM Latency Formula

$$\text{Latency (ns)} = \frac{\text{CAS}}{f_{\text{clock}}} \times 2000 = \text{CAS} \times \frac{2000}{\text{Data Rate (MT/s)}}$$

For DDR memory, data rate in MT/s is twice the clock speed in MHz. A DDR4-3200 kit with CL22 has latency $22 \times 2000 / 3200 = 13.75$ ns.

Reading Memory Module Labels

A label like 8GB DDR4-3600 CL-16-19-19-36 means 8 GB capacity, DDR4 generation, 3600 MT/s data rate, and CAS latency of 16 clock cycles. The other numbers are tRCD, tRP, and tRAS timing values.

Related tools: Download Time Calculator and Bandwidth Calculator.

Frequently Asked Questions

Is lower CAS latency always better?

Lower CAS at the same data rate means lower nanosecond latency. However, higher-speed kits often have higher CL numbers but still achieve competitive or better real-world latency.

What is a good RAM latency?

Most modern DDR4 and DDR5 kits fall between 8 and 20 ns. Under 10 ns is excellent; 13–15 ns is typical for mainstream DDR4.

What is the difference between MHz and MT/s?

DDR transfers data twice per clock cycle, so 3200 MT/s equals a 1600 MHz clock. Retail listings sometimes show MT/s values labeled as MHz.

Does RAM latency matter for gaming?

Yes, especially for CPU-bound games and high frame rates. The impact is smaller than capacity or speed tier but noticeable when comparing similar kits.

Can I mix RAM with different CAS timings?

It may work but is not recommended. The system typically runs all modules at the slowest common settings, reducing performance of faster sticks.

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What Is RAM Latency?

DDR RAM Latency Formula

Reading Memory Module Labels

Frequently Asked Questions

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