The short answer. A farm carbon audit estimates what the farm emits. It takes the records you already keep, such as fertiliser, fuel, feed and livestock numbers, and runs them through a calculator. Soil carbon measurement samples the soil to show whether the carbon it holds is rising or falling, field by field, with the error stated. An audit tells you where your emissions come from. Measurement tells you what your soil is actually doing. They answer different questions, and more and more farms will be asked for both.
Last reviewed September 2026.
What a farm carbon audit does
A carbon audit, often called a carbon footprint, adds up the greenhouse gases from the farm over a year. The activity data comes from your records, and the calculator multiplies each activity by an emission factor to give tonnes of carbon dioxide equivalent (tCO2e) for the whole farm, for each enterprise and often for each tonne of product.
That is genuinely useful. It shows where the emissions sit, which on most farms means nitrogen fertiliser, livestock, purchased feed and fuel, so you know what is worth tackling first. Calculators widely used in the UK include Agrecalc, the Cool Farm Tool, the Farm Carbon Calculator and the Solagro carbon calculator.
What a calculator cannot tell you
A calculator does not sample your soil. Where it includes carbon stored in the soil at all, it estimates it from the practices you enter, from default values or from an organic matter figure you give it. That can be a fair guide, but it is not a measurement of your fields, and it cannot show a bad year in the year it happens. Different calculators can also give different answers for the same farm, because they use different emission factors and draw the boundary of the farm in different places.
What soil carbon measurement adds
Soil carbon measurement starts in the field. Physical samples are analysed by dry combustion in a laboratory accredited to ISO/IEC 17025 and tied to satellite imagery at 100 mapped values a hectare, with the error measured against samples the AI never saw and deducted. It is repeated once a year, in the autumn-winter window, against your own baseline. The result is the change in soil organic carbon stock for each field, which is the side of the ledger a calculator can only estimate.
| Farm carbon audit | Soil carbon measurement | |
|---|---|---|
| The question it answers | What does the farm emit, and where from? | Is the carbon in my soil rising or falling? |
| How it works | Farm records and emission factors in a calculator | Soil samples, laboratory analysis and satellite mapping |
| Soil carbon | Estimated, if included | Measured, field by field, with the error stated |
| How often | Up to the farm, and at least every five years under Scotland’s Whole Farm Plan | Every year, at the same point in the year |
| What it is used for | Finding emission hotspots, benchmarking, scheme and supply chain requests | Management decisions, supplier-specific removals data, and credits |
| Can it support carbon credits? | Not on its own | Yes, under a registry methodology, with emissions deducted |
Where the rules ask for which
- Scotland. Under the Whole Farm Plan, farmers and crofters claiming the Basic Payment Scheme must have at least two of five audits and plans in place, and all of those relevant to the business by 15 May 2028. One is a carbon audit, aligned to PAS 2050 or part of a UK supply chain contract and updated at least every five years. Another is soil sampling of Region 1 land at least once every five years, and any analysis from 1 July 2024 onwards must include soil carbon.
- Wales. The Sustainable Farming Scheme opened on 1 January 2026. Its soil health action asks for soil testing, including soil organic matter, on at least 20% of improved land a year, and the scheme sets a farm level carbon baseline from the information farms provide.
- Supply chains. Food and drink companies are starting to ask their suppliers for farm-level data, and the GHG Protocol land sector standard many buyers will use from 2027 expects emissions and removals to be reported separately. A footprint covers the emissions. Measured soil carbon change is what stands behind the removals.
Which one you need
- A scheme or a buyer asks for your carbon footprint. A carbon audit.
- You want to know whether your soil is gaining or losing carbon. Soil carbon measurement.
- A buyer wants removals reported alongside emissions. Both: the emissions from an audit or a full emissions calculation, and the removals from measurement.
- You want to sell soil carbon credits. Measurement to a registry methodology, with the farm’s emissions deducted.
The two work well together. The audit shows what to cut. The measurement shows what the soil is doing, and whether the changes you make are working.
How Ecometric fits
- Measure. Soil carbon measurement, field by field, every year, with the accuracy stated. You can start here.
- Report. Adds an IPCC Tier II emissions calculation, to the GHG Protocol land sector standard many buyers will use from 2027: both sides of the ledger, what the farm emits and what it removes.
- Credits. Issued for each tonne sequestered after greenhouse gas emissions are deducted, under our published methodology on the Regen Registry.
Every round is measured to the full Registry standard whichever tier you are on, so adding emissions reporting or credits later is a decision rather than starting again. More in soil carbon measurement for farms.
Questions we are asked about farm carbon audits
What is a farm carbon audit?
An estimate of the greenhouse gases a farm emits over a year, worked out in a calculator from farm records such as fertiliser, fuel, feed and livestock numbers. It shows the total, and where the emissions come from.
Is a carbon audit the same as a carbon footprint?
In farming the two terms are used for the same thing. The audit is the process, and the footprint is the result, in tonnes of carbon dioxide equivalent.
Does a farm carbon calculator measure soil carbon?
No. A calculator works from records and emission factors. Where it includes soil carbon, it estimates it. Measuring soil carbon takes physical samples, laboratory analysis and enough coverage to show each field, repeated at the same point every year.
Which carbon calculators can be used for the Whole Farm Plan in Scotland?
The Scottish Government guidance lists Agrecalc Cloud, the Cool Farm Tool, the Farm Carbon Calculator and the Solagro (JRC) carbon calculator. The audit must be aligned to PAS 2050 or be part of a UK supply chain contract. Check the current guidance on the Rural Payments and Services website before you choose.
How often does a farm carbon audit need doing?
For Scotland’s Whole Farm Plan, at least every five years. Some farms repeat theirs every year to track progress. Soil carbon is different: to see a real change, it has to be measured every year at the same point in the year.
Can a carbon audit be used to sell carbon credits?
Not on its own. Soil carbon credits need a measured change in soil carbon under a registry methodology, independently verified. With Ecometric, credits are issued for each tonne sequestered after greenhouse gas emissions are deducted.
How do I get my soil carbon measured?
Send us your SBI number and your hectares and we will send a written quote within two working days. Minimum project area is 150 hectares, and it does not have to be your whole farm. Get a quote.
Part of our guide to soil carbon measurement for farms. Related: soil health testing in the UK · soil carbon testing methods compared · soil carbon credits for UK farmers
