Memory Utilization Calculator
Calculate real memory utilization from /proc/meminfo values, correctly excluding buffers and cache that the kernel can reclaim.
Inputs
Used Memory
7,680.0MB
Usage Percentage
46.88%
Available Memory (free+buffers+cached)
8,704.0MB
Available Percentage
53.13%
Status
Healthy
Step by step
Values used
MemTotal = 16,384 MB; MemFree = 2,048 MB; Buffers = 512 MB; Cached = 6,144 MB
Used memory
used = total − free − buffers − cached
Usage percentage
usage% = used / total × 100
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
How it works
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
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.