Quick answer
This calculator answers a specific question: how many nanoseconds do advertised DDR4 or DDR5 timing values represent? With the default profiles, DDR5-6000 CL30 is 10.00 ns and DDR4-3600 CL16 is 8.89 ns, so Kit B has 1.11 ns lower CAS true latency.
Use it for: comparing timing profiles on a common time scale. Do not use it alone for: predicting application performance, memory-overclock stability, or platform compatibility.
How to use the calculator
- Read the profile as data rate followed by timings, for example DDR5-6000 30-36-36-76.
- Enter 6000 as Kit A MT/s, then enter 30, 36, 36, and 76 in CL, tRCD, tRP, and tRAS.
- Enter a second profile for Kit B. Use the profile the computer will actually run, not a faster profile the platform cannot support.
- Compare CAS first, then tRCD, tRP, and tRAS. Treat small differences as tie-breakers after capacity, price, support, and stability.
What the results mean
- Cycle time: the duration of one memory clock cycle after converting the DDR transfer rate.
- CAS true latency: the delay represented by CL, useful for the headline comparison.
- tRCD and tRP: row-to-column and row-precharge timing intervals on the same nanosecond scale.
- tRAS: the minimum row-active interval represented by the profile label.
- Difference: which kit has lower CAS true latency and by how many nanoseconds; it is not a whole-system performance percentage.
Decision notes for this calculator
How to interpret this calculator
Use the CAS latency result first, then compare tRCD, tRP, and tRAS when two kits have similar advertised speed or CL values. Treat very small differences as tie-breakers, not as the whole buying decision.
Sources and assumptions
The calculation follows the standard latency relationship: elapsed time equals clock cycle time multiplied by timing cycles. DDR labels are entered as MT/s, so the clock-period conversion uses 2000 divided by data rate.
- Crucial: memory speed, CAS latency, and true latency
- NIST: SI prefixes and nanosecond units
- CalculatorShelf source guide: storage and hardware formulas
Method version: MEMORY_TIMING-1.2. Send corrections through the contact page.
What to do next
Compare the nanosecond result with motherboard QVL notes, CPU memory-controller limits, capacity needs, XMP or EXPO support, and stability reports for the exact kit.
Save this scenario
Use Share, Copy result, or Print / PDF to keep the exact inputs with the result. If something looks wrong, report an issue with the Memory Timing Calculator.
What this RAM timing calculator compares
CL values cannot be compared fairly without data rate. This tool combines both parts of a DDR profile and converts CL, tRCD, tRP, and tRAS to nanoseconds for two kits.
- Required inputs: advertised data rate in MT/s and four primary timing-cycle values.
- Side-by-side outputs: cycle time, CAS true latency, tRCD/tRP latency, tRAS latency, and the CAS difference.
- Best decision use: distinguish genuinely lower timing latency from a lower-looking CL number.
- Important boundary: it does not estimate bandwidth, subtiming effects, gaming frame rates, or memory-training success.
For adjacent decisions, compare graphics memory needs, removable storage capacity, or file transfer time.
Sensitivity hint: MT/s changes the cycle time used for every row; each timing-cycle value then scales its own result directly.
Use the timing profile the computer will actually run
A retail kit may advertise an XMP or EXPO profile while a system starts at a slower JEDEC profile. Compare the values active in BIOS or operating-system hardware information when you want to understand the current system.
- Before buying: confirm CPU generation, motherboard memory support, module type, capacity, and the qualified-vendor list where available.
- After installation: confirm the applied MT/s and timings, then run an appropriate stability check before relying on an overclocked profile.
- When profiles tie: two kits can have the same CAS nanoseconds while differing in bandwidth, capacity, price, secondary timings, or platform support.
Formula and unit method
DDR data-rate labels report millions of transfers per second. Because double-data-rate memory transfers on both clock edges, the clock period is cycle time (ns) = 2000 ÷ data rate (MT/s). Convert any timing with timing latency (ns) = timing cycles × cycle time (ns).
Example: DDR5-6000 CL30 gives 2000 ÷ 6000 = 0.333 ns per cycle, then 30 × 0.333 = 10.00 ns. Enter 6000 MT/s, not the 3000 MHz base clock.
Assumptions and limitations
- DDR data rate is entered as transfers per second in MT/s, not base memory-clock MHz.
- The formula treats the timing labels as cycle counts and does not model subtimings, gear mode, command rate, memory channels, cache behavior, or workload-specific bottlenecks.
- XMP and EXPO profiles may need BIOS support and stable voltage settings; if a system runs default JEDEC timings, use those actual timings instead.
- For laptop, server, or workstation purchases, capacity and compatibility can matter more than a small latency difference.
Worked RAM timing examples
| Profile | Cycle time | CAS true latency | What it shows |
|---|---|---|---|
| DDR5-6000 CL30 | 0.333 ns | 10.00 ns | Higher CL can still reach 10 ns at a high data rate. |
| DDR4-3600 CL16 | 0.556 ns | 8.89 ns | Lower CAS latency in the default comparison. |
| DDR5-6400 CL32 | 0.313 ns | 10.00 ns | Same CAS nanoseconds as DDR5-6000 CL30, with a different data rate. |
| DDR5-5600 CL36 | 0.357 ns | 12.86 ns | A higher data rate does not guarantee lower CAS true latency. |
For the default full timing labels, DDR5-6000 30-36-36-76 converts to 10.00 / 12.00 / 12.00 / 25.33 ns. DDR4-3600 16-19-19-39 converts to 8.89 / 10.56 / 10.56 / 21.67 ns.
Common mistakes
- Comparing CL alone without converting to nanoseconds.
- Entering base clock MHz instead of the advertised DDR data rate in MT/s.
- Ignoring whether the motherboard and CPU can run the selected XMP or EXPO profile.
- Assuming a small timing advantage beats more capacity for memory-heavy workloads.
RAM timing FAQ
How do you convert CL to nanoseconds?
Divide 2000 by the DDR data rate in MT/s, then multiply by CL. DDR5-6000 CL30 is 30 × (2000 ÷ 6000) = 10.00 ns.
Why can DDR5 CL30 and DDR4 CL16 have similar latency?
DDR5 often uses more timing cycles but has a shorter cycle time because its data rate is higher. Nanoseconds combine those two effects.
What do tRCD, tRP, and tRAS mean here?
They are additional profile timing intervals measured in memory clock cycles. This calculator puts each one on the same nanosecond scale; it does not model every subtiming or workload interaction.
Can I compare two RAM kits on this page?
Yes. Enter the profile values for Kit A and Kit B. The results show both kits side by side and identify the lower CAS true latency.
Do lower nanoseconds always mean a faster PC?
No. Capacity, channels, bandwidth, CPU cache, controller limits, motherboard support, subtimings, stability, and workload behavior can matter more than a small difference.
Should I enter JEDEC, XMP, or EXPO timings?
Enter the profile the computer will actually run. Use XMP or EXPO values only when the CPU and motherboard support that profile and the system is stable; otherwise enter the active JEDEC or BIOS values.
Method details
Updated: July 17, 2026. Calculation method: MEMORY_TIMING-1.2. Availability: interactive calculator.