Calculating Magic Damage

Actual Damage
Actual Damage is calculated by multiplying the following factors in order and flooring after each step. 1) D 2) Multiple-Target Damage Reduction 3) resist 4) Staff Bonus 5) Day | Weather Bonus 6) Magic Burst Bonus 6a) Magic Burst Bonus Gear #1 6b) Magic Burst Bonus Gear #2 7) MAB / MDB 8) Target Magic Damage Adjustment

There is reason to believe that the magic burst portion is calculated prior to MAB. Further testing would be necessary to confirm the order of the other parts with respect to magic bursts.

Calculation of D
Each magic tier has an inherent mutliplier value M. Each magic spell has a base value V. Let dINT be (Caster's INT - Target's INT). (Banishes and Holy, substitute MND for INT).

For dINT < 0: D = V + dINT (when dINT is a penalty, the tier mult. is always 1) For dINT > 0, but less than some inflection point: D = V + (dINT * M) For dINT > 0, but after some inflection point: D = V + (const + (dINT-const) * M / 2)) (above some critical value, adding INT becomes half as effective) For dINT > 0, but after some cap: D = cap

M = 1.0 for all tier I/II single-target spells. M = 1.0 for all -ga spells up to Blizzaga II. M = 1.0 for all Ichi and Ni tier Ninjitsu spells. M = 1.5 for all San tier Ninjitsu spells. M = 1.5 for all tier III single-target spells. M = 1.5 for all -ga spells Thundaga II and beyond. M = 2.0 for all tier IV and Ancient Magic spells.
 * M = 1.0 for Holy.
 * M = 1.0 for all Helix spells.

V values by spell:

Multiple-Target Damage Reduction
single-target spells = 1.0 -ga spells with one target = 1.0 -ga spells with 2 through 9 targets = 0.9 - 0.05T where T is the number of targets -ga spells with 10 or more targets = 0.4

Resist
resist = 1, 1/2, 1/4, 1/8, or 1/16

Staff Bonus
HQ Staff matching element = 1.15 NQ Staff matching element = 1.1 No staff = 1.0 NQ Staff ascendant element = 0.9 HQ Staff ascendant element = 0.85

Day of the Week | Weather Bonus
Day | Weather Bonus is calculated as: plus approximately a 1/3 chance for one of the following: plus approximately a 1/3 chance for one of the following: The day and weather components are guaranteed to take effect when wearing an obi matching that day or weather. Helix spells calculate day and weather bonuses at 100% at all times regardless of equipment. Weather spells do stack with natural weather and day but not beyond the natural cap of 20 for double weather and 10 for day. Also of note is this effect can work against you as weather and day of the opposing element will negatively impact your helix damage even with weather of the supporting element active in the spell form. This term is capped at 1.35, even in the presence of day, double weather, and Sorcerer's Tonban.
 * 1.0
 * +0.05 for Sorcerer's Tonban when magic matches the current day.
 * +0.1 for magic of the day
 * -0.1 for magic weak to the current day
 * +0.1 for magic matching single weather
 * -0.1 for magic weak to single weather
 * +0.25 for magic matching double weather
 * -0.25 for magic weak to double weather

Magic Burst Bonus
MB bonus is 1.0 for no MB and 1.3 for a 2-WS renkei, gaining 5% per extra WS in the renkei series (i.e. 1.35, 1.4 etc) Sorcerer's Gloves multiply the magic burst bonus by 1.05. Static Earring multiplies the magic burst bonus by 1.05. ex. ''floor(floor(floor(floor(... * MB) * Sorc.Gloves) * St.Earring) * ...)'' -> ''floor(floor(floor(floor(... * 1.3) * 1.05) * 1.05) * ...)''

Magic Attack Bonus / Magic Defense Bonus
MAB is divided by MDB.

MAB is as we know it (i.e. MAB I = 1.2, MAB II = 1.24 etc). Items with the description "Magic Atk. Bonus"+X means to add X/100 to the current MAB. For example, Moldavite Earring which states "Magic Atk. Bonus"+5 means to add 0.05. Correct element potency merits are +2 MAB per merit, which adds 0.02.

MDB is 1.0 if not present and depends on the target of the magic.

After calculating the ratio of MAB to MDB, this term is truncated to two decimal places.

Target Magic Damage Adjustment
Target Magic Damage Adjustment means exactly what it sounds like. Certain targets are designed to take more or less % damage. Values for this portion of the equation appear to use the 256 number system. The base value is 1 (256/256) and is adjusted according to the fractional values in the charts below. The values are added together in the presence of more than one adjustment. ex. Ahriman have a TMDA value of (1 - 64/256) = 192/256 ex. An Evil Weapon with Shell has a TMDA value of (1 - 32/256 - 24/256) = 200/256 Note: For player targets, this value is capped at 128/256 (50%).

Helices
Follow the same rule as above but the Damage dealt is repeated a number of times in 10 second intervals. Weather seems to have little to no effect on duration.