Mobile Signal Strength Explained: dBm vs ASU (Including 5G) for Everyday Users

Have you ever checked your phone’s signal info and seen numbers like -88 dBm, 14 ASU, or terms like RSRP/SS-RSRP and wondered what they mean? Signal strength is something we rely on constantly, but the way it’s measured can feel confusing—especially with 5G. Here’s a clear breakdown.

Why Signal Strength Is More Than “Bars”

• Signal bars are just a visual estimate, not precise measurements.
• Two phones showing the same bars can have very different actual signal levels.
• Numeric values like dBm or ASU give a more accurate picture of your connection.

dBm: The Universal Signal Strength Number

• dBm (decibel-milliwatts) measures radio signal power.
• Values are always negative, which is normal.
• The closer the number is to zero, the stronger the signal.

Typical ranges:

• Around -60 dBm: excellent, fast speeds, reliable calls.
• Around -80 dBm: solid for everyday use.
• Around -95 dBm: slower speeds, occasional issues.
• Below -105 dBm: unstable connection.

If you want one number that works across all modern networks, dBm is the most reliable.

ASU: Arbitrary Strength Unit

• ASU is a simplified scale, usually shown on Android devices.
• Uses small positive integers instead of negative numbers.
• Higher ASU means stronger signal.
• Conversion to dBm depends on whether the phone is on 3G, 4G, or 5G.

ASU is best seen as a relative indicator. For precision, dBm is the better measure.

Signal Strength on 5G

5G introduces terms like SS-RSRP (Reference Signal Received Power).

• Still measured in dBm.
• Same rule applies: closer to zero is better.

Sub-6 GHz 5G:

• Most common form of 5G today.
• Behaves similarly to LTE in terms of signal strength.
• Strong signal usually means better speeds and lower latency.

mmWave 5G:

• Extremely fast but very sensitive to obstacles like walls, trees, or even your hand.
• Signal drops quickly with distance.
• Phones often fall back to LTE or Sub-6 when mmWave is weak.

Why 5G Can Feel Unstable

• Phones switch between LTE, Sub-6, and mmWave silently in the background.
• These handoffs can cause brief slowdowns or fluctuations.
• Performance depends on network deployment, available spectrum, and congestion.
• Sometimes a strong LTE signal can outperform a weak 5G signal.

Signal Strength vs Signal Quality

Signal strength alone doesn’t tell the full story.

• Strong signal can still mean slow speeds if the network is congested.
• Moderate signal can perform well if the spectrum is clean.
• Other factors like interference, bandwidth, and signal-to-noise ratio matter too.

dBm vs ASU: Which Should You Trust?

• dBm is consistent, precise, and universal across technologies.
• ASU is simplified and useful for quick reference, but less exact.

Shortcut to remember:

• Strong signal → dBm closer to zero, ASU higher.
• Weak signal → dBm very negative, ASU lower.

Final Thoughts

Whether you’re on LTE or 5G, understanding dBm and ASU gives you real insight into your connection beyond the bars. 5G adds speed and complexity, but the fundamentals of radio signal strength remain the same. Once you know the numbers, it’s easier to tell if slow performance is due to weak signal, obstacles, or network congestion.