Mbps vs MBps: Why Your Download Looks Slower Than Your Plan

Updated 2026 · 4 min read

It's the most common source of confusion in internet speeds: your plan says 100 Mbps but files download at around 12 MB/s. Both numbers are correct — they're just different units.

Bits vs bytes

Mbps = megabits per second (lowercase b). MB/s = megabytes per second (uppercase B). There are 8 bits in a byte, so you divide by 8: a 100 Mbps connection delivers about 12.5 MB/s at best.

Why ISPs advertise in Mbps

Bigger-sounding number. "100 Mbps" markets better than "12.5 MB/s," even though they're identical. Speed tests (including this one) report in Mbps to match your plan; download managers usually show MB/s.

Quick conversion table

• 25 Mbps ≈ 3.1 MB/s
• 100 Mbps ≈ 12.5 MB/s
• 300 Mbps ≈ 37.5 MB/s
• 1 Gbps (1000 Mbps) ≈ 125 MB/s

Why you rarely hit the full number

WiFi overhead, the server's own limits, network congestion and protocol overhead all shave off real-world throughput. Getting 85–95% of your plan on a wired connection is normal and healthy.