Angle is measured from flat: 0 is horizontal, 90 is straight up.
Wet grain: pick the OSU calculator and enter moisture (14 is dry, 25 is very wet, anything in between is blended), or the Randy method, which takes the dry motor size and multiplies it by 1.5. Leave RPM blank to compare speeds. Enter the auger pulley and it shows the motor sheave for each speed. Enter the motor sheave and it shows the auger pulley. Enter both and it works out the RPM and the motor size for you. If the auger runs through a gearbox, set the gearbox ratio (leave it at 1 for none).
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Recommended motor (HP)
Where the numbers come from. Power and capacity for 4 to 10 in augers come from Oklahoma State University Extension BAE-1105 (shelled corn, from Purdue Research Bulletin 740). The tests were run at set speeds and at 0, 45 and 90 degrees. The tool blends between them, and between 14% and 25% moisture, in straight lines. 12 and 14 in augers. No public test data exists for these sizes. They use the OSU 4 to 10 in data scaled up by diameter cubed, then compared against what other makers and testing groups have published. Treat them as estimates. How the motor size is worked out. HP per foot from the data x auger length x 1.10 (for belt and drive losses). Soybeans add 40%. The result is rounded up to the next standard motor size. For wet grain you can pick the OSU calculator (university wet tests, uses moisture) or the Randy method (the dry motor size x 1.5, rounded up to the next motor). The Randy method is a shop shortcut, not test data. Why it leans high. Compared with the manufacturer tables checked, this calculator usually asks for a bit more HP (about 5% to 20% more for 6 to 10 in, and more for 12 and 14 in). That is on purpose, so the motor is less likely to come up underpowered.
This is an estimate for planning only, not a rating. Before you buy a motor, check with the auger manufacturer and with the manufacturer of the equipment you are installing it on.