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1.15 Ratios & Percentages

RATIOS

A ratio is a proportional relationship of one value to another, e.g., the ratio of gas to oil in chain saw mix. Ratios can be written either as a fraction, 1/2, or in ratio notation, 1:2. The value of a ratio is the division of the first number by the second number. For example, consider the ratio 1:40 . This ratio is read as "1 to 40". Any fraction, for instance, 1/20, can also be written as a ratio: 1:20

Example 1 - The Mara Bella District has 6 engines. The Baldy District has 5 engines. What is the ratio of engines in the Mara Bella versus the Baldy districts? 

The ratio of engines in the Mara Bella versus Baldy districts is 6:5 or 6/5.
 

PERCENTAGES

A percentage is another way of describing a ratio with respect to 100. Percent (%) is a value corresponding to how many out of a hundred (per hundred). For instance, if 92 out of 100 firefighters have completed the FireFighter Math course, the ratio of firefighters completing the course is 92:100, and the percentage is written as 92%.

Example 2 - Write four notations for 56.8%.

56.8% = 56.8 out of 100
56.8% = 56.8/100
56.8% = 56.8:100
56.8% = 0.568 (Note that performing this calculation results in moving the decimal two places to the left because there are two zeros in 100.)
 

PERCENTAGES AND LIVE FUEL MOISTURES

Percentages are useful for a number of fire science applications. One of these applications is estimating live fuel moisture. Live fuel moisture can be measured using oven drying and weighing procedures. Because this process is time-consuming and cannot be completed in the field, fire considerations are usually satisfied with a good estimate. Live fuel moisture can be estimated using the values in the figure below, which provides moisture percentages for fuels at different stages of vegetative development. For instance, from the figure, we observe that completely cured fuels have a live fuel moisture of less than 30%. This value is the result of subtracting the dry weight of the fuel from the total (wet) weight and dividing by the dry weight. 

Live Fuel Moisture %
 

Example 3 - A fuel sample collected in the field weighs 377 grams. After the sample is dried in an oven, it weighs 198 grams. What is the live fuel moisture content?

Step 1. Subtract the dry weight from the wet weight. 377 - 198 = 179.

Step 2.Divide the difference by the dry weight and multiply by 100 to find the value as a percent. 179 / 198 × 100 = 0.904 × 100 = 90.4%. 

The live fuel moisture of your sample is 90.4%. 
 

PROBLEM SOLVING WITH RATIOS

When solving a more complex percentage or ratio problem, write the problem down in words and numbers and work through one step at a time.

 

NWCG Latest Announcements

Updated NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515

Date: April 23, 2025
Questions?  Please contact:
Interagency Fire Unmanned Aircraft Systems Subcommittee

The NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515 standardizes processes and procedures for the interagency use of Unmanned Aircraft Systems (UAS), including pilot inspections and approvals. This updated publication provides the aviation community with standards to ensure UAS are used safely, effectively, and efficiently in support of fire management goals and objectives.

References:

NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515

NWCG National Interagency Aviation Committee

ETC Bulletin 25-001: Retrofitted Hot/Cold Beverage Kits - 2025 Field Season

Date: April 16, 2025
Questions?  Please contact:
Equipment Technology Committee

Due to spout failures and the associated risk of burn injuries, manufacturers have retrofitted the Hot/Cold Beverage Kits using a heat-shrinking band to secure the black spout at the insertion site. The updated kits feature a fluorescent label on each full kit assembly for easy identification. Catering units are encouraged to confirm the clear heat-shrinking bands are intact around each spout before filling.

ETC Bulletin 24-001 regarding Hot/Cold Beverage Kits has been archived and replaced by ETC Bulletin 25-001 for the 2025 season.

References:

NWCG Alerts

ETC-EB-25-001 Retrofitted Hot/Cold Beverage Kits

NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212, and Next Generation Position Task Book for Basic Faller Are Now Available

Date: April 14, 2025
Questions?  Please contact:
Hazard Tree and Tree Felling Subcommittee

The updated NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212, and NWCG Position Task Book for Basic Faller (FAL3), PMS 311-19 are now available.

The NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212 includes position standards designed to be used in conjunction with the Next Generation Position Task Book (Next Gen PTB). The Next Gen PTB for Basic Faller (FAL3) includes an evaluation guide with suggested rating elements to consider when assessing trainees.

References:

NWCG Standards For Wildland Fire Chainsaw Operations, PMS 212

NWCG Position Task Book for Basic Faller (FAL3), PMS 311-119

NWCG Basic Faller (FAL3)

RMC Memo 25-01: Summary of Updates to Safety Officer Positions

Date: April 9, 2025
Questions?  Please contact:
RMC Member Eric Fransted

The Risk Management Committee (RMC) serves as the position steward for all Safety Officer incident positions and continues to improve position standards, training, and naming conventions. The implementation of Complex Incident Management (CIM) required changes to position titles. RMC collaborated with the NWCG Incident Position Standards Committee (IPSC) to propose and implement these updates. 

References:

RMC Memo 25-01: Summary of Updates to Safety Officer Positions 

NWCG Position Catalog