# Specific absorption rate (SAR)

> Watts of RF power absorbed per kilogram of tissue — the dosimetric quantity behind phone compliance testing, limited to 1.6 W/kg over 1 g in the U.S. and 2 W/kg over 10 g under ICNIRP.

- Canonical URL: https://emfbase.com/quantities/specific-absorption-rate
- Collection: Quantities & units
- Record id: `quantities:specific-absorption-rate`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/quantities/specific-absorption-rate
- Also known as: SAR, W/kg

## Key values

- **Symbol:** SAR
- **SI unit:** W/kg
- **Units in use:** W/kg, mW/g, mW/kg

## What it measures

Energy absorption in tissue during near-field exposure, measured in a liquid-filled phantom at maximum transmit power. Because the U.S. averages over 1 g and ICNIRP over 10 g, the two published numbers for the same phone are not comparable.

## Units

Multiplier to the SI unit (W/kg).

- **W/kg (watt per kilogram)** — 1 W/kg = 1 W/kg
- **mW/g (milliwatt per gram)** — 1 mW/g = 1 W/kg
- **mW/kg (milliwatt per kilogram)** — 1 mW/kg = 0.001 W/kg

## Related records

- [FCC SAR limit for phones and portable devices](https://emfbase.com/limits/fcc-sar-limit-phones): 1.6 W/kg averaged over any 1 gram of tissue — the number quoted on U.S. phone SAR sheets — plus 0.08 W/kg whole-body.
- [ICNIRP 2020 local SAR basic restriction (head and torso)](https://emfbase.com/limits/icnirp-local-sar-limit): 2 W/kg averaged over 10 grams of tissue for the general public — a different averaging mass than the FCC's 1 g, which is why SAR numbers are not directly comparable between regions.

## Sources

- `fcc-2-1093` U.S. Government Publishing Office (eCFR). *47 CFR § 2.1093 — Radiofrequency radiation exposure evaluation: portable devices*. https://www.ecfr.gov/current/title-47/section-2.1093 — regulation, link checked 2026-08-12
- `icnirp-2020` International Commission on Non-Ionizing Radiation Protection (2020). *Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz)*. https://www.icnirp.org/en/publications/article/rf-guidelines-2020.html — guideline, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.