RAM Latency Calculator
Convert CAS latency and RAM speed to real nanosecond latency. Compare two RAM kits side-by-side and discover which is actually faster — because DDR5's higher MHz number doesn't always mean lower latency.
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Kit B
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Kit A
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nanoseconds
Kit B
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nanoseconds
Bandwidth Context
Theoretical single-channel bandwidth. DDR5 DIMMs have two 32-bit channels internally, doubling effective bandwidth.
Common RAM Kits — Reference Table
| Kit | Speed | CL | Latency (ns) | Rating |
|---|
Why MHz Alone Doesn't Tell You RAM Speed
RAM marketing uses MHz (or MT/s) as the headline number, but it only tells half the story. The other half is CAS latency (CL) — the number of clock cycles the RAM takes to respond to a request. At higher clock speeds, each cycle is shorter, so CAS latency in nanoseconds requires the formula: (CL × 2000) ÷ Speed MT/s. This reveals the shocking truth: a DDR5-4800 CL40 kit (16.67ns) is 67% slower in real latency than DDR4-3600 CL16 (8.89ns) — despite having a higher MHz on the box. Always calculate nanoseconds before comparing any two kits. Last updated: March 2026.
DDR5 vs DDR4 Latency — The Real Numbers
The DDR5 generation transition reveals a recurring pattern: early or budget DDR5 kits often have worse real-world latency than well-tuned DDR4. DDR5-4800 CL40 at 16.67ns is worse than DDR4-2666 CL18 at 13.50ns. However, high-end DDR5 kits flip the script: DDR5-6000 CL28 at 9.33ns and DDR5-7200 CL34 at 9.44ns beat even the best DDR4 kits. The sweet spot for DDR5 on AMD AM5 is 6000 MT/s at CL30 or lower, which matches the 2:1 Infinity Fabric ratio. On Intel platforms, 7200–8000 MT/s at low CL delivers the best results.
How CAS Latency Affects Gaming and Workloads
Lower nanosecond latency means the CPU waits less time for data from RAM. In gaming at 1080p with fast CPUs (Ryzen 7 7800X3D), latency differences of 2–3ns can translate to 3–8% FPS differences in CPU-limited scenarios. At 1440p and 4K, the GPU becomes the bottleneck and RAM latency impact shrinks to 1–3%. For content creation — video rendering, 3D animation, large dataset operations — bandwidth (GB/s) often matters more than latency, where DDR5's higher bandwidth wins decisively. For programming and general use, differences under 1ns have no perceptible impact.
How to Choose the Best RAM for Your Budget
Prioritize value-per-nanosecond, not MHz-per-dollar. For DDR4 systems: DDR4-3600 CL16 hits the sweet spot (8.89ns at reasonable cost). Avoid DDR4 over 4000 MHz unless overclocking — the cost premium rarely pays off. For DDR5 on AM5: target 6000 MT/s at CL28–CL30 (around $80–120 for 32GB as of March 2026 after recent price drops). Avoid budget DDR5 kits below DDR5-5600 CL36 — their latency is worse than DDR4. For content creation, prioritize capacity (32GB or 64GB) over speed, since bandwidth scales with capacity in dual and quad-channel configurations.