Enemy Level Scaling

All enemies that you encounter in Warframe have a certain level, which determines their strength by increasing some of their base statistics. The stats amplified by enemy level gain are Health, Armor, Shield, Damage and Affinity. The purpose of this article is to show how exactly these stats scale with level, how this translates to useful indicators such as effective health, and what implications this has towards player decision making such as aura or damage type selection.

Common Features of Stat Scaling
How scaling of fundamental enemy stats works in general is identical for all the stats: Each enemy type has a base value for this fundamental stat and a base level, the current value of the stat at the current level of the enemy is then calculated after a formula of the following structure:

Current Value = Base Value * ( 1 + ( Current Level - Base Level )Exponent * Coefficient )

Exponent and coefficient are determined by the specific stat in question, but are equal across all enemy types. Base level and base value of the stat are determined by the enemy type (i.e. its name). Current level is then the independent variable and current value of the stat is the dependent variable of the formula.

The coefficient is usually much smaller than one. Therefore, the level scaling of stats is barely noticeable at lower levels. For high levels, the exponent is the most impactful when comparing different scaling stats against each other. If the exponent is 1, the scaling of the stat would be linear with level, which means the increase in value as level grows would be constant. For exponents higher than 1, each successive levelup grants a larger increase than the previous one, and for exponents lower than one, each successive levelup grants a smaller increase than the previous one.

This so far only applies to fundamental stats, i.e. health, armor, shields, damage and affinity. Derived stats, e.g. effective health, are calculated by incorporating multiple of these fundamental stats, which is covered further below. Fundamental stats are stats in the narrower sense, so if "stats" is not specified, fundamental stats are meant.

Scaling of Fundamental Stats
As mentioned, all fundamental stats scale by the above formula structure and common features apply. A standardized graph is shown for each stat. When comparing the graphs, the different Y-axis scaling has to be considered.

Health
The formula for health scaling is:

Current Health = Base Health * ( 1 + ( Current Level - Base Level )2 * 0.015 )

Shields
The formula for shield scaling is:

Current Shield = Base Shield * ( 1 + ( Current Level - Base Level )2 * 0.0075 )

Armor
The formula for armor scaling is:

Current Armor = Base Armor * ( 1 + ( Current Level - Base Level )1.75 * 0.005 )

Damage
The formula for damage scaling is:

Current Damage = Base Damage * ( 1 + ( Current Level - Base Level )1.6 * 0.013 )

Affinity
The formula for the scaling of affinity/XP granted upon kill of the enemy is:

Current Affinity = Base Affinity * ( 1 + ( Current Level - Base Level )0.5 * 0.1425 )

Synopsis
In the previous figures, the Y-axis was fit to the value space of the shown function. To get an idea of the proportions compared to the other stats, here are all of them in one figure:

Scaling of Derived Stats
From these fundamental stats, more meaningful stats can be derived.

Effective Hitpoints
Effective Hitpoints is a stat that indicates how many gross damage has to be applied to a target until the net damage thereby inflicted depletes its entire health. Effective Hitpoints is not a fixed stat for any given enemy, it is heavily altered by the damage type used against the target, as well as many buffs and debuffs applied to the attacker or the target, hitzone hit, etc. For the following considerations however, these influences are disregarded, as they do not alter the course of the graphs except for clinching or stretching them as a whole, which manifests like a scaling of the Y-axis.

For Enemies with Health only
For targets without shields and armor, the standardized effective hitpoint scaling is synonymous with standardized health scaling, the health graph and formula apply.

For Enemies with Health and Shield
The standardized effective hitpoints of shielded enemies is simply the sum of their shields and health, except for the case when the Toxin portion of the gross damage depletes the target's health faster than the rest of the gross damage depletes its shield. Exact effective hitpoint calculations considering damage types also become significantly more complex if Toxin damage is involved, but this is disregarded here. The level scaling of standardized effective hitpoints of shielded enemies is influenced by the ratio of base shields to base health, with higher shield portions meaning weaker standardized scaling. However, this may be considered an artifact of standardization, as in actuality, shield and health simply scale independently from each other and are summed up to the total amount of effective hitpoints. It only means that for the same sum of base health and shield, a higher portion of health will mean better level scaling than a lower portion of health. Regarding the formula, while both are just added to each other, it can be simplified since health and shield share the same exponent:

Current Effective Hitpoints = ( Base Health + Base Shield / 2 ) * ( 1 + ( Current Level - Base Level )2 * 0.015 ) + Base Shield / 2

For Enemies with Health and Armor
Health and armor synergize in increasing effective hitpoints, as opposed to health and shield which stack only. This makes the effective hitpoint development of armored enemies extremely steep, outclassing that of shielded unarmored enemies significantly, which is why Grineer are considered harder to play against than Corpus at high levels.

The two figures show the exact same set of functions, just with different kinds of Y-axis scaling. The different graphs are for different values of net base armor, i.e. the base armor of the enemy type after the reduction from Corrosive Projections and after mitigation for a certain damage type, if applicable. a0 is an unarmored line for comparison. The used formula is:

Current Effective Hitpoints = Current Health * ( 1 + Current Armor / 300 )

With Current Health and Armor taken from the respective formulae.

The large impact of the net base armor vividly visualizes how important damage type modifiers against armor armor types and Corrosive Projection are at high levels.

For Enemies with Health, Shield and Armor
The effective hitpoints of enemies with health, shield and armor are the sum of the effective health (i.e. current health and armor incorporated as in the previous formula for armored enemies) and the shield. There is no new aspect to this, but standardization in this case is not opportune, as it requires a specification for both the base shield to health ratio and base armor amount, there are more of these combinations than actual enemy types these apply to, and effective hitpoints for shielded and armored enemies may therefore rather be calculated for any specific enemy that fits this category, which goes beyond the scope of this article. Obvious just from comparing the large values of effective hitpoints (armored) to the values of shield alone, the armored health portion of the total effective hitpoints heavily outscales the shield portion, which implies it is generally advantageous to select damage types after the armor's vulnerabilities rather than the shield's vulnerabilities for high level shielded armored enemies. For more accuracy, effective hitpoint portions have to be calculated for specific enemies.

Shielding Ratio
The shielding ratio of shielded, unarmored enemies is the ratio of their shield to their health. Since health and shield scale by different coefficients, this ratio changes with level. In fact, the ratio converges against half of its base value, albeit slowly so over common level ranges. The shielding ratio is relevant for two things: Evaluating and selecting damage types against shielded enemies, i.e. weighing benefits against shield types against benefits against health types, and the scaling behavior of Mag's Shield Polarize.

Affinity Density
The affinity density of an enemy is its affinity per effective hitpoints and a measure of its profitability for affinity (i.e. experience or reputation) farming. It is important to note the actual affinity farming profitability is significantly offset off the optimal area as implied by the affinity density function due to the two important practical influences of overkill and retargeting time, which both contribute to shifting the actual optimum from these implications towards higher levels, by a significant but hardly quantifiable amount.

Reflective Kill Rate
Reflective kill rate of an enemy is the ratio of its damage output and effective hitpoints. This is inversely proportional to the amount of time or attacks an enemy would need to kill another of its kind. It's a measurement for the effectivity of damage reflecting effects and abilities, such as the Radiation proc, the Reflection mod, and abilities such as Link, Shadows of the Dead, Absorb, Chaos or Mind Control. As you can see, while the absolute damage output of damage reflection abilities does scale with enemy level (see damage scaling figure), it is nevertheless being outscaled by enemies' health and therefore relatively decreasing. As a result, while these abilities do become increasingly impactful with higher levels, they are still insufficient to kill enemies within limited time indefinitely.

Currentness of the Formulae
The scaling formulae of Warframe have previously been subjected to stealth changes, i.e. without mention in the patch notes, as has been the damage formula. They may be re-verified from time to time.