# Decibel (dB) Calculator

Calculate sound level in decibels from intensity. Combine dB levels from multiple sources. Free online dB calculator with power ratio conversion.

## What this calculates

The decibel (dB) is a logarithmic unit used to express the ratio of a sound intensity to a reference level. This calculator converts sound intensity to decibels using dB = 10 log₁₀(I/I₀), where I₀ = 10⁻¹² W/m² is the standard threshold of human hearing. You can also combine two dB levels to find the total sound level from multiple sources.

## Inputs

- **Sound Intensity** (W/m²) — min 0 — Reference: 10⁻¹² W/m² (threshold of hearing)
- **Reference Intensity** (W/m²) — min 0 — Standard reference: 10⁻¹² W/m²
- **First dB Level (for combining)** (dB)
- **Second dB Level (for combining)** (dB)

## Outputs

- **Sound Level** (dB) — dB = 10 × log₁₀(I / I₀)
- **Combined dB Level** (dB) — Result of combining two sound sources
- **Power Ratio** — I / I₀ — ratio of intensity to reference

## Frequently Asked Questions

**Q: Why do we use decibels instead of regular units?**

A: The range of sound intensities humans can hear spans about 12 orders of magnitude (from 10⁻¹² to 1 W/m²). A logarithmic scale compresses this enormous range into a manageable 0–120 dB scale. It also better matches how our ears perceive sound, since perceived loudness increases roughly logarithmically with intensity.

**Q: How much louder is a 10 dB increase?**

A: A 10 dB increase represents a tenfold increase in sound intensity. However, humans perceive a 10 dB increase as roughly twice as loud. A 3 dB increase doubles the intensity, a 20 dB increase means 100 times the intensity, and a 30 dB increase means 1,000 times the intensity.

**Q: Can you just add decibel levels together?**

A: No. Because decibels are logarithmic, you cannot simply add them. Two 60 dB sources produce about 63 dB, not 120 dB. To combine dB levels, you must convert each to linear intensity, add the intensities, then convert back to dB. This calculator handles that conversion for you.

**Q: What are typical dB levels?**

A: Common reference points: whisper ≈ 30 dB, normal conversation ≈ 60 dB, vacuum cleaner ≈ 70 dB, city traffic ≈ 85 dB, rock concert ≈ 110 dB, jet engine at 30 m ≈ 140 dB. Prolonged exposure above 85 dB can cause hearing damage.

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Source: https://vastcalc.com/calculators/physics/decibel
Category: Physics
Last updated: 2026-04-21