---
title: "What is NBR? (Normalized Burn Ratio) & dNBR Burn Severity"
description: "NBR measures fuel condition and fire risk; dNBR measures burn severity after a fire. Learn both formulas, the USGS severity scale, and how satellites assess wildfire damage."
url: https://www.agroreports.org/articles/what-is-nbr/
lang: en
updated: 2026-06-18
source: https://www.agroreports.org/articles/what-is-nbr/
license: All rights reserved. (c) AgroReports
---

# What is NBR? (Normalized Burn Ratio)

## What is NBR?

NBR, the **Normalized Burn Ratio**, is a satellite index tuned to detect burned vegetation and assess fuel condition before a fire. It uses the same near-infrared band as NDVI but pairs it with a deeper shortwave-infrared band (SWIR2) that is especially sensitive to ash, charred material, and dry woody fuel.

It serves two distinct purposes: **NBR** (single snapshot) measures current vegetation dryness and fuel condition — low NBR means dry, fire-prone vegetation. **dNBR** (differenced NBR) compares pre-fire and post-fire NBR to measure how badly an area burned — this is the standard used by fire agencies worldwide.

## How it's calculated

Healthy vegetation reflects strongly in near-infrared and absorbs shortwave-infrared. Burned or very dry vegetation does the opposite: NIR reflectance collapses and SWIR2 reflectance rises. NBR turns this contrast into a number:

```
NBR = (NIR − SWIR2) / (NIR + SWIR2)
```

On Sentinel-2 these are **Band 8** (NIR) and **Band 12** (SWIR2, ~2.2 µm). The ratio structure normalizes brightness across scenes.

For the differenced version used after a fire:

```
dNBR = NBR_pre-fire  −  NBR_post-fire
```

A larger positive dNBR means a more severe burn — the canopy lost more of its healthy reflectance between the two dates.

## Typical value ranges

Pre-fire NBR for fuel condition and fire risk:

| NBR range | Meaning | Fire risk |
|----------|---------|-----------|
| **> 0.4** | Lush, wet vegetation | Very low |
| **0.2 – 0.4** | Healthy vegetation | Low |
| **0.0 – 0.2** | Drying vegetation | Moderate |
| **−0.1 – 0.0** | Dry, stressed | High |
| **Below −0.1** | Very dry / burned / bare | Extreme |

Post-fire dNBR burn severity (USGS standard):

| dNBR range | Severity class | What it means on the ground |
|------------|---------------|------------------------------|
| **< 0.1** | Unburned / enhanced | Vegetation regrowth or no burn |
| **0.1 – 0.27** | Low severity | Surface fire, canopy largely intact |
| **0.27 – 0.44** | Moderate–low severity | Partial canopy mortality |
| **0.44 – 0.66** | Moderate–high severity | Heavy canopy mortality |
| **> 0.66** | High severity | Stand-replacing fire, total canopy loss |

## When to use it

Use NBR for pre-fire risk assessment: low values before fire season indicate dry, flammable fuel. Combine with NDMI (moisture) for a complete fuel-condition picture. Use dNBR after a fire to classify burn severity for insurance claims, reforestation planning, and erosion risk assessment.

For dNBR, pre-fire image selection matters critically. Trustworthy pipelines select cloud-free imagery 5–90 days before the fire and 5–60 days after. Before 5 days, smoke contaminates the image; after 60 days, fast vegetation recovery can mask the true severity. Other land-cover changes (logging, harvest, senescence) can also lower NBR — a real burn assessment cross-references the timing of the drop against the fire event.

## Comparison with other indices

NBR is the fire-specialist index. NDMI measures leaf water content (primary fire risk indicator), while NBR measures fuel condition and burn severity — the two complement each other in fire-danger scoring. NDVI tracks green canopy density and recovers after fire, but NBR is far more sensitive to char and ash because of the SWIR2 band. For post-fire damage assessment, dNBR is the international standard that NDVI and NDMI cannot replace.

> **Try it free:** Get NBR values for your field — free, no signup. Works on any land worldwide. [Assess my land's fire risk or burn impact →](/)

## Frequently asked questions

<details>
<summary>What is the difference between NBR and dNBR?</summary>

**NBR** is a single snapshot of current vegetation condition — low values indicate dry, fire-prone fuel. **dNBR** is the *difference* between a pre-fire and post-fire NBR image, used to measure **how severely an area burned**. NBR is for risk assessment before a fire; dNBR is for damage assessment after.
</details>

<details>
<summary>What is a good dNBR value?</summary>

There is no "good" dNBR — lower is less severe. **Below 0.1** is considered unburned or enhanced (regrowth). **0.1–0.27** is low-severity surface fire. **Above 0.66** is high-severity, stand-replacing fire. The USGS classification is the international standard.
</details>

<details>
<summary>Can NBR predict wildfires?</summary>

Not on its own. NBR measures fuel condition — how dry and flammable the vegetation is — but ignition depends on weather, human activity, and lightning. NBR (fuel) combined with NDMI (moisture) and weather data gives a meaningful risk score, but no satellite index predicts ignition.
</details>

<details>
<summary>How soon after a fire can I assess burn severity?</summary>

Typically **5–60 days after** the fire date, once the smoke has cleared and before significant regrowth or senescence distorts the reading. Before 5 days, smoke and active fire contaminate the image; after 60 days, fast vegetation recovery can mask the true severity.
</details>