Eighth Mile Calculator
Convert eighth-mile ET and MPH to quarter-mile equivalents.
Many tracks are eighth-mile, but quarter-mile times are the universal benchmark. This calculator converts your 1/8-mile ET and trap speed into estimated quarter-mile figures using established conversion factors.
1/8 to 1/4 Mile Conversion
These multipliers work well for most street and strip cars. Very high-powered or traction-limited cars deviate slightly, since the second half of the quarter mile depends on power and aero more than the launch.
How to Use This Calculator
- Enter your eighth-mile ET in seconds.
- Optionally enter eighth-mile trap MPH.
- Read the quarter-mile estimates.
Worked Example
Why Convert Eighth-Mile to Quarter-Mile
Many drag strips — especially smaller or street-legal venues — run an eighth-mile (660 ft) instead of the full quarter (1,320 ft), often for safety or space. But the quarter mile remains the universal benchmark for comparing cars and bench-racing. These conversion factors let you translate an eighth-mile timeslip into a comparable quarter-mile ET and trap speed without making a full pass.
When the Conversion Is Most Accurate
The 1.557 ET and 1.25 MPH multipliers work well for typical street and bracket cars that pull cleanly through the traps. They drift for two kinds of cars: very high-powered machines still accelerating hard at the eighth (which gain more in the back half), and traction-limited cars that struggle off the line. Treat the result as a close estimate, not a guaranteed quarter-mile number.
Eighth-to-Quarter Conversion Examples
| 1/8 ET | 1/8 Trap | Est. 1/4 ET | Est. 1/4 Trap |
|---|---|---|---|
| 7.0 s | 98 MPH | 10.9 s | 123 MPH |
| 8.5 s | 85 MPH | 13.2 s | 106 MPH |
| 10.0 s | 70 MPH | 15.6 s | 88 MPH |
Frequently Asked Questions
Multiply the eighth-mile ET by about 1.557. For example, an 8.5-second eighth-mile is roughly a 13.2-second quarter-mile.
Multiply the eighth-mile trap speed by about 1.25. So 85 MPH at the eighth becomes roughly 106 MPH at the quarter.
Eighth-mile tracks need less land and are safer for street cars and bracket racing, so they're very common, especially in some regions.
They're good estimates for typical cars, usually within a few tenths and a few MPH. High-power or low-traction cars can deviate more.
Yes — convert to quarter-mile figures first, then use the trap-speed or ET horsepower calculators.