Skip to main content

5.2 Map Scale

The map scale is printed in the map legend. It is given as a ratio of inches on the map corresponding to inches, feet, or miles on the ground. For example, a map scale indicating a ratio of 1:24,000 (in/in), means that for every 1 inch on the map, 24,000 inches have been covered on the ground. Ground distances on maps are usually given in feet or miles. 
 

Map Scale Conversion Factors

 

Scale Representative Fraction Map in/mi Map in/ch map ft/in
1:253,440 253.44 0.25 0.0031 21,120
1:126,720 126.72 0.50 0.0063 10,560
1:63,360 63.36 1.00 0.0125 5,280
1:62,500 62.50 1.01 0.0127 5,208
1:31,680 31.68 2 0.025 2,640
1:24,000 24.00 2.64 0.033 2,000
1:21,120 21.12 3 0.038 1,760
1:15,840 15.84 4 0.05 1,320
1:7,920 7.92 8 0.1 660

Table 5.1. Map Scale Conversion Factors

Example 1 - Convert the map scale of 1:24,000 (in/in) to (in/ft).

Step 1. Set up the cancellation table so all units will cancel, except the desired unit, ft/in.

cancellation table

On the map 1 inch is equal to 2,000 feet on the ground, 1:2,000 (in/ft).

Example 2 - Convert the 1:2,000 (in/ft) to (in/mile).

Step 1. Set up the cancellation table so all units will cancel, except the desired unit, miles/inch.

cancellation table

On the map 1 inch is equal to 0.4 miles.

Example 3a - The map distance between two points is 6 inches. The map scale is 1:24,000 (in/in). What is the ground distance in feet?

Set up the cancellation table so all units will cancel, except the desired unit, feet.

cancellation table

The ground distance is 12,000 feet.

USING THE MODIFIED ACREAGE GRID (TRANSPARENCY)

To use the acreage grid transparency, follow these steps:

acreage grid
 

Map Scales and Equivalents

Scale Inches per mile Acres per square inch Conversion factor that each dot equals
1:20,000 3.168 63.769 1.736 Acres
1:24,000 2.640 91.827 2.500 Acres
1:62,500 1.014 622.449 16.946 Acres
1:63,360 1.000 640.000 17.424 Acres

Table 5.2 Acreage Grid Overlay, Map Scales, and Equivalents.

  1. Place the acreage grid transparency over the area to be measured.
  2. Count dots inside the sketched area. Count every other dot when dots fall on the boundary line.
  3. Multiply the total number of dots by the conversion factor on the map scale to determine the total acreage. (See Table 5.2.)
  4. Example 3b - Using the information in Example 3a, find the ground distance in chains, miles, and inches.

    Step 1. Set up the cancellation table so all units will cancel, except the desired unit, chains.

    cancellation table

    12,000 feet = 182 chains
     

    Step 2. Set up the cancellation table so all units will cancel, except the desired unit, miles.
    cancellation table

    Step 3. Set up the cancellation table so all units will cancel, except the desired unit, inches.
    cancellation table
    12,000 feet = 182 chains = 2.3 miles = 144,000 inches

    Occasionally, a map may not provide a scale. The scale can be calculated by knowing the distance between two points on the map, and measuring the distance on the map. Also, if a map has section lines, the distance between section lines is typically 1 mile.

    Example 4 - The distance between point A and B is 6 inches on the map. The known ground distance is 3,600 feet. What is the scale in units of inches/foot?

    The map scale is 1:600 inches/foot.

    Example 5 - Use the map scale in example 6. The known ground distance between points B and C is 1/2 mile. How many inches is does this distance correspond to on the map?

    map scale = known distance / measured distance

    Rearrange terms by multiplying each side by the measured distance and dividing each side by the map
    scale.

    measured distance = known distance / map scale

    Step 1. Set up the cancellation table so all units will cancel, except the desired unit, feet.

    cancellation table

    Step 2. Use the map scale from Example 6 to find the map distance.

    measured distance = known distance
    map scale
    measured distance = 2,640 feet 1 inch = 4.4 inches
    600 feet

    On the ground one-half mile is the same as 4.4 inches on the map.









  5.  
  6.  
  7.  
  8.  
  9.  
  10.  
  11.  

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