Eighth-mile time, speed and quarter-mile equivalent
1/8 Mile ET Calculator
Many tracks and events run an eighth mile (660 ft), including most street-legal and small-track drag nights. Enter your weight and horsepower to get an eighth-mile ET and speed instantly.
- Quarter-mile ET
- 12.55 sec
- Quarter-mile trap
- 108.6 mph
- Distance
- 660 ft
- Weight per hp
- 10.00 lb/hp
- Multiplier (time)
- 1.560 ×
- Multiplier (speed)
- 1.25 ×
How the 1/8 mile estimate is made
We first predict the quarter-mile ET and trap speed, then scale them to the shorter distance: the 1/8-mile time is about 64% of the quarter-mile time (the usual 1.56 multiplier in reverse), and the 1/8-mile speed is about 80% of the quarter-mile speed (the 1.25 multiplier in reverse).
With 3,200 lb and 320 hp the 1/8-mile estimate is 8.04 s at 86.9 mph. Those multipliers are documented in Stealth316’s horsepower / ET / MPH calculator notes.
Convert a real slip to a quarter-mile time
If you have already made an eighth-mile pass, use the converter above. A 7.50 s run at 90 mph projects to about 11.70 s at 112.5 mph over the full quarter. The projection is generous when you are traction limited, because you have no idea yet what the second half will bring.
Eighth-mile time by power-to-weight
Here is a lookup table using the formula for a 3,500 lb car:
| Horsepower | 1/8 mile ET | 1/8 mile speed |
|---|---|---|
| 200 hp | 9.69 s | 72.1 mph |
| 300 hp | 8.47 s | 82.5 mph |
| 400 hp | 7.69 s | 90.8 mph |
| 500 hp | 7.14 s | 97.9 mph |
| 600 hp | 6.72 s | 104.0 mph |
| 800 hp | 6.11 s | 114.5 mph |
Frequently asked questions
How many feet is an eighth mile?
An eighth of a mile is 660 feet, 220 yards or about 201 metres. See feet in a 1/8 mile.
What is a good 1/8 mile time?
It depends on the class, but because a rule of thumb says quarter-mile ET is roughly 1.56 times the eighth-mile ET, a 7.50 s eighth-mile pass lines up with about an 11.7 s quarter.
Do both numbers scale the same way?
Time scales by about 1.56 and speed by about 1.25 between the eighth and the quarter. See the 1/8 to 1/4 mile conversion chart.
Related calculators
QuarterMile Pro
$9 one-time
- No ads, ever
- Saved runs and your garage
- CSV export of every estimate
- Embeddable calculator widget for your site
Placeholder only: Pro is not on sale yet, and there is nothing to buy or sign up for. Every calculator here stays free.
Not available yet