Memory Utilization Calculator
Calculate overall memory utilization percentage across physical RAM and swap.
About Memory Utilization Calculator
Linux aggressively uses spare RAM for disk buffers and page cache because reclaiming that memory for an application is essentially free and instantaneous. Naively looking at MemFree alone therefore overstates memory pressure. Real used memory subtracts buffers and cached (which the kernel will happily hand back on demand) from the total, alongside free memory, giving a truer picture of what applications actually hold.
Formulas
Used memory
used = total − free − buffers − cached
- T
- MemTotal
- F
- MemFree
- B
- Buffers
- C
- Cached
Usage percentage
usage% = used / total × 100
Worked example
With the default values below, Memory Utilization Calculator returns Used Memory of 7,680.0. Change any input above and every figure here is recalculated in your browser.
Inputs used
- MemTotalminimum 0 MB
- 16,384 MB
- MemFreeminimum 0 MB
- 2,048 MB
- Buffersminimum 0 MB
- 512 MB
- Cachedminimum 0 MB
- 6,144 MB
Results
- Used Memory
- 7,680.0 MB
- Usage Percentage
- 46.88%
- Available Memory (free+buffers+cached)
- 8,704.0 MB
- Available Percentage
- 53.13%
- Status
- Healthy
Step by step
- 1Values used
- 2Used memory
- 3Usage percentage
- 4Used Memory= 7,680.0 MB
- 5Usage Percentage= 46.88
- 6Available Memory (free+buffers+cached)= 8,704.0 MB
- 7Available Percentage= 53.13
- 8Status= Healthy
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does `free -m` show so little free memory even when the system feels fine?
Because Linux fills spare RAM with disk cache and buffers to speed up repeated I/O. That memory is reclaimed instantly if an application needs it, so it should be counted as available, not used — which is exactly what modern `free` output's 'available' column reflects.
Is this the same as the MemAvailable field in /proc/meminfo?
It's a simplified approximation. The kernel's MemAvailable estimate also accounts for reclaimable slab memory and watermarks, so it can differ slightly from a plain free+buffers+cached sum, but the concept is the same.
At what usage percentage should I worry?
Sustained usage above 85-90% of real (non-cache) memory is a common warning threshold, since it leaves little room before the OOM killer or heavy swapping kicks in under a load spike.