Bore / Stroke Ratio Calculator
Bore divided by stroke. Above 1.00 is oversquare and likes revs; below 1.00 is undersquare and makes low-end torque.
| Bore / stroke ratio | 1.1494 | : 1 |
- ratio = bore ÷ stroke
When you need it
When you are choosing between two ways of reaching the same displacement — a big bore with a short stroke, or a smaller bore with a long one.
What it tells you
An oversquare engine (ratio above 1.00) has room for larger valves and less shrouding around them, and it keeps piston speed down at a given RPM. That combination is why oversquare engines rev.
An undersquare engine (below 1.00) trades that for crank leverage and cylinder filling at low RPM. It makes torque earlier, but piston speed climbs faster with RPM, so the useful ceiling arrives sooner.
Do not read too much into it
The ratio is descriptive, not destiny. Cylinder head flow and cam timing decide where an engine makes power far more than bore and stroke do. A long-stroke engine with good heads will out-rev a square one with poor ones.
Treat this as one input among several. For judging how hard a combination is working, mean piston speed is the more useful number.