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© Peter Ogden, 2007

GearCalc v2.0.0.3

for Windows 95/98/NT/2000/XP

Freeware, Copyright ©2003, Peter Ogden

The user is authorised to download, copy and/or distribute at no charge. Peter Ogden retains copyright on the source code. The user must not disassemble or reverse engineer GearCalc.

Please note: Due to a series of unfortunate circumstances (a disk crash and concurrent backup failures), I no longer have the source code to modify this program further. I apologise to all those people that would like the facility to model 8 speed gearboxes and the like. I cannot add these features without starting from scratch, and I no longer have the spare time to spend on this.

GearCalc is a program that calculates theoretical maximum speeds in each gear and speed per 1000 RPM (revolutions per minute), given the maximum RPM of the engine (redline), the gear ratios, tyre size and the differential ratio. It also produces a chart of RPM values for every 10 Km/h increment in metric mode or every 5 MPH increment and gear up to the redline. Finally, it also calculates the rev drop at each gear change.

Entry of tyre size can be in the 185/70x14 style, which will then automatically calculate the diameter and circumference, or if the tyre is not marked in this style of sizing, actual measurement of diameter or circumference (the most accurate method) can be entered.

The user should be aware that the maximum speeds calculated here do not take into account wind resistance. Often, a vehicle will not achieve the calculated maximum speed in top gear as there is insufficient power to overcome wind resistance. GearCalc can assist with choosing an appropriate gear set to maximise performance.

Pre-configured gear sets include: Ford types 9/N, C, H, a large section of Brian G Hill (BGH) Geartech and Quaife Gear sets, Honda Prelude and Civic, some Nissan 4 and 5 speed boxes, Mazda MX5 (Miata), Mitsubishi 3000GT, a large selection of Toyota Gearboxes and Transaxles, a large list of VW gearboxes, Cosworth and Caterham gear sets. Now added MGB gearsets (thanks to Deane Mundy).


  • Calculates maximum speed at "redline" in each gear and speed per 1000 RPM
  • Chart of RPM's for each gear at 10 Km/h (or 5 Mph) intervals
  • Calculates rev drop and actual RPM value at each gear change
  • Calculations performed in Metric or Imperial units
  • The chosen units are maintained between runs
  • Pre-set gear sets or manual input (additional gear sets added)
  • Comparative gear ratios displayed graphically
  • Compound ratios calculated and displayed for each gear
  • Results can be saved to a text file or printed
  • If known, you can enter the RPM at which peak power is generated and you can then compare shift points at max RPM and Peak Power (leave blank if not known)
  • Defaults to last entered values at program start
GearCalc Thumbnail (14.5k) - Click to see Full Size (53.9k)

Download GearCalc (516k)

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See sample output (for above input): Sample.txt (2.8k)
or download it: (1k)