Bicycle gears are traditionally expressed in "gear inches." To understand gear inches think back to the high wheeler days. The bigger front wheel, the faster you could ride. When the safety bicycle was invented with a chain drive and wheels the same size, the formula for gear inches was invented so that its gearing could be compared with that of a high wheeler.
To get gear inches, first count the number of teeth on each sprocket on your bike.
Gear inches for a road bike= the number of teeth on the front chainring / the number of teeth on the rear cog x 27 inches. Do that for every gear combination on your bike and you'll find out there is considerable overlap in the gearing available for each of the front chainrings.
Gear ratios higher than 100 gear inches are very fast. Many riders can't use then effectively unless they are going downhill. Gear ratios in the 30 gear inch range are only useful on road bikes for climbing hills. Mountain bikes often have hill climb gears in the low 20 gear inch range.
To get an easier hill climbing gear, you need to put either a bigger cog on the back or get a smaller chainring for the front. Practically speaking, it's usually easier to change the rear cogs.