Technology
Allowing for real-world efficiency
Divides the effective speed rather than the advertised one. An efficiency of 0.92 models overhead, contention and server limits in a single number.
The Formula
t_real = size / (speed x eff)
Divides the effective speed rather than the advertised one. An efficiency of 0.92 models overhead, contention and server limits in a single number.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| size | File size | megabits | Still in megabits. |
| speed | Advertised speed | megabits per second | The headline rate on the plan. |
| eff | Efficiency | dimensionless | Fraction of the advertised rate actually achieved. |
What Each Symbol Means
sizemegabits
File size
Still in megabits.
speedmegabits per second
Advertised speed
The headline rate on the plan.
effdimensionless
Efficiency
Fraction of the advertised rate actually achieved.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate download time page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Download Time, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.