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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

NEW! NWCG Standards for Airtanker Operations, PMS 514

Date: March 7, 2025
Contact: National Interagency Aviation Committee

The NWCG Standards for Airtanker Operations, PMS 514 establishes the standards for dispatching, utilizing, and coordinating airtankers on interagency wildland fires. These standards should be used in conjunction with the NWCG Standards for Aerial Supervision (SAS), PMS 505, NWCG Standards for Airtanker Base Operations (SABO), PMS 508, and any applicable agency plans.

References:

NWCG Standards for Airtanker Operations, PMS 514

Incident Position Standards and Next Gen Position Task Books Now Available for Dispatch Incident Positions

Date: March 5, 2025
Contact: National Coordination System Committee

NWCG is excited to announce that Incident Position Standards and Next Generation Position Task Books are now available for all six Dispatch positions:

  • Aircraft Dispatcher
  • Expanded Dispatch Coordinator
  • Expanded Dispatch Recorder
  • Expanded Dispatch Supervisory Dispatcher
  • Expanded Dispatch Support Dispatcher
  • Initial Attack Dispatcher

The Performance Support Packages for these positions, including the Expanded Dispatch Job Aid, J-601 and the Initial Attack and Aircraft Dispatcher Job Aid, J-602, were developed as part of the Incident Performance and Training Modernization (IPTM) effort. These resources support trainees, qualified personnel, and evaluators in their roles.

Any changes to qualification pathways will take effect with the next update of the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1.

References:

NWCG Aircraft Dispatcher Position Page 

NWCG Expanded Dispatch Coordinator Position Page 

NWCG Expanded Dispatch Recorder Position Page 

NWCG Expanded Dispatch Supervisory Dispatcher Position Page 

NWCG Expanded Dispatch Support Dispatcher Position Page 

NWCG Initial Attack Dispatcher Position Page 

NWCG Job Aids 

Incident Position Standards and the Next Generation Position Task Books Now Available for DMOB, DOCL, and RESL

Date: February 28, 2025
Contact: Incident Operations Subcommittee

NWCG is excited to announce that Incident Position Standards and the Next Generation Position Task Books are now available for Demobilization Unit Leader (DMOB), Documentation Unit Leader (DOCL), and Resources Unit Leader (RESL).

The Performance Support Packages for these positions, including a job aid for RESL, were developed as part of the Incident Performance and Training Modernization (IPTM) effort. These resources support trainees, qualified personnel, and evaluators in their respective roles.

Any changes to qualification pathways will take effect with the next update of the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1.

References:

NWCG Demobilization Unit Leader Position Page 

NWCG Documentation Unit Leader Position Page 

NWCG Resources Unit Leader Position Page 

Next Generation Position Task Book and Updated Incident Position Description Now Available for Operations Section Chief Complex

Date: February 27, 2025
Contact: Incident Operations Subcommittee

NWCG is excited to announce that Operations Section Chief Complex (OSCC) has a Next Generation NWCG Position Task Book for Operations Section Chief Complex (OSCC), PMS 311-108 and an updated Incident Position Description.

These resources support trainees, qualified personnel, and evaluators in their respective roles.

References:

NWCG Operations Section Chief Complex Position Page 

NWCG Operations Section Chief Complex Incident Position Description 

NWCG Position Task Book for Operations Section Chief Complex (OSCC), PMS 311-108