# VM0047 additionality calculator

Last updated: 2026-11-01

Run one part of Verra VM0047’s additionality assessment for a reforestation (ARR) project: the Z test and performance benchmark for area-based projects, or the 15% common-practice test for census-based ones, with what the benchmark leaves of measured growth.

Open the tool: https://restorationscope.com/tools/vm0047-additionality-calculator (free, no account).

Read more: [Additionality for reforestation projects, explained](https://restorationscope.com/blog/additionality-reforestation-projects).

## How it works

1. Choose area-based or census-based, the two ways VM0047 counts a project’s trees.
2. Area-based: enter the stocking-index slopes and standard errors your remote-sensing provider reports for project and control plots. Census-based: enter the survey counts.
3. Read the verdict, the numbers behind it and what it means in credits. Try the pass and fail examples to see where the line sits.

## Input and output

- Input: Area-based: the yearly stocking-index slope and its standard error for your project plots and their matched control plots, and optionally the measured carbon stock change and its 90% confidence half-width. Census-based: how many similar landowners you surveyed and how many already do the activity without carbon finance.
- Output: Pass or fail, the Z score, the control slope VM0047 uses, the performance benchmark and the share of growth credited, and the stock change left after the benchmark and uncertainty deduction; or the adoption rate against the 15% common-practice line.

## Example

Input:

```text
Project slope 0.04 (SE 0.006) · control slope 0.01 (SE 0.004) · stock change 12,000 t CO2e · half-width 18%
```

Output:

```text
Passes: Z = 4.16 (|Z| ≥ 1.96), performance benchmark 0.25, 75% of growth credited
12,000 × 0.75 × (1 − 8%) = 8,280 t CO2e
With a control slope of 0.032 (SE 0.006): Z = 0.94, not significant, benchmark 1, no growth counts
```

## Limits

- It runs the arithmetic in VM0047 v1.1 (Appendix 1 Equations A7 and A8, Equations 28 and 32, Section 7.3.4). It does not build the stocking index, pick or match the control plots, or check the match.
- It reads a control slope as significant when it is at least 1.96 standard errors from zero, the large-sample form of VM0047’s P ≤ 0.05. With few control plots your regression’s own P-value decides.
- The credit figure is Equation 32’s cumulative term, which is the result for a first verification: every verification subtracts project emissions and leakage, later ones also subtract the previous verification’s full result, and the buffer contribution comes after that.
- Both approaches also need regulatory surplus. Census-based projects always need an investment analysis (VT0008 Step 3), area-based ones only with revenue or financial incentives other than carbon credit sales. It runs neither.
- Your validation and verification body decides whether the project is additional.

## Privacy

Everything runs in your browser. Your files are never uploaded to our servers.

## Questions

### How does VM0047 test additionality for area-based projects?

With a dynamic performance benchmark. Each project plot is matched to control plots outside the project that looked the same in satellite data before it started. At every verification the yearly growth in stocking index of both groups is compared with a Z test. If the project grew significantly faster (|Z| of 1.96 or more), the benchmark is the control slope divided by the project slope, and the rest of the measured growth can be credited.

### What happens if the Z test fails?

If project and control plots don’t differ significantly (|Z| below 1.96), the performance benchmark is set to 1 and no growth counts. Equation 32 subtracts the previous verification’s result, so a fail right after a credited verification is negative. The project is not cancelled: the test runs again at the next verification with every year of monitoring so far.

### What is the common-practice test for census-based projects?

The share of similar landowners in the defined geographic area who already do the project activity, with data from within five years of the start date: from a representative survey, counting those without carbon finance, or from qualifying public statistics, which count all adopters. At 15% or more it is common practice and not additional. Census-based projects also need regulatory surplus and an investment analysis.

### Is my data uploaded anywhere?

No. The calculation runs in your browser, and the numbers you enter stay there.