Ive hated this formula and avoided it for about 5 years. I just buckled down and figured it out, and actually its pretty easy providing we are using default K values K1=1 and K3=1 (i.e. BW and Delay,) are used for the metric. The entire metric formula can actually just become BW + Delay. Bare with me, see the math below:

The actual formula is below

Metric=[K1* BW + (K2*BW)/(256*load) + K3 * Delay]

Since K2 = 0, this means the whole line of (K2*BW)/(256*load) can be completely removed (because 0 divided by anything is 0). So the formula becomes

Metric= K1*BW + K3*Delay

Since K1=1 and K3=1, the formula can be simplified again to

Metric= BW + Delay

So thats it. Although there is a catch, which is how all the exam questions always try and catch you out. In the EIGRP metric calculation, the BW is not actually the BW & the delay is not actually the delay. How annoying is that? See below

Bandwidth = Inverse lowest bandwidth along a path in Kbps x 10^7 * 256.

Delay = Lowest cumulative delay along the path x 256

My first question was, what the heck is inverse bandwidth? Actually it just means 1/BW. Let do a real life example of the calculation then. Take a look at the show output below, we will calculate how EIGRP came up with the metric as being 28160 for this network.

UKINTR1#sh ip eigrp topology 200.70.80.0/24

EIGRP-IPv4 Topology Entry for AS(100)/ID(10.66.255.1) for 200.70.80.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 28160

Descriptor Blocks:

0.0.0.0 (GigabitEthernet0/1), from Connected, Send flag is 0x0

Composite metric is (28160/0), route is Internal

Vector metric:

Minimum bandwidth is 100000 Kbit

Total delay is 100 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 0

Originating router is 10.66.255.1

So we simplified the metric formula to BW + Delay. Weve only got 2 values to work out, so lets start by working out the bandwidth.

Bandwidth = Inverse lowest bandwidth along a path in Kbps x 10^7 x 256.

Bandwidth = 1/100000 x 10^7 x 256

Bandwidth = 25600

Now lets work out the delay

Delay = Lowest cumulative delay along the path x 256

Delay = 10 x 256 (remember delay is in Tens of Microseconds, whereas the output above shows only microseconds).

Delay = 2560

Now lets put this into the Metric

Metric = BW + Delay

Metric = 25600 + 2560

Metric = 28160