Armor Weight

Turn armor progression into a choice between protection and mobility.

ITM's Armor Weight calculates the weight of each equipped item from its Armor, Armor Toughness, and Knockback Resistance attributes.

Every player has a configurable Armor Weight Capacity. Equipment within that capacity causes no slowdown; excess weight gradually reduces movement speed.

Because the system uses standard item attributes instead of a hardcoded material list, vanilla and modded armor participate automatically.

Features

• Attribute-based weight for vanilla and modded armor.
• Configurable Armor Weight Capacity.
• No movement penalty while total weight remains within capacity.
• Smooth overload-based slowdown rather than fixed armor tiers.
• Optional Max Health scaling for capacity.
• Item tooltips preview weight, capacity, and projected slowdown.
• Server-controlled gameplay settings synchronized with clients.
• Support for Forge, NeoForge, and Fabric.

What players will notice

Armor Weight turns equipment progression into a practical tradeoff:

• Wear light equipment for mobility and easier disengagement.
• Accept moderate weight for reliable all-purpose protection.
• Build around heavy armor and reduced movement speed.
• Mix armor pieces instead of automatically choosing the highest available stats.

Early and mid-game armor generally remains within the default capacity. Diamond and netherite introduce a modest mobility cost, while exceptionally heavy modded equipment can produce much stronger penalties.

Default balance

The default Armor Weight Capacity is 20. Full leather, gold, chainmail, and iron sets all fit within that capacity and therefore cause no slowdown.

The table assumes the default capacity, with Max Health scaling disabled.

These values are examples, not hardcoded special cases. The modded rows use the armor's default Minecraft 1.20.1 item attributes and are calculated piece by piece rather than from the player's aggregated armor bar:

• Terrasteel: 20 total Armor, 12 total Toughness, and 1.0 total Knockback Resistance
• Dragonsteel: 34 total Armor and 24 total Toughness
• Refined Obsidian: 31 total Armor, 20 total Toughness, and 0.8 total Knockback Resistance

Other mod versions or modpack configurations may change those attributes and therefore produce different weights.

How item weight is calculated

For the positive additive Armor (A), Armor Toughness (T), and Knockback Resistance (K) attributes of one item:

pieceWeight =
    A * armorImpact
      * (1 + T * toughnessImpact)
      * (1 + K * knockbackResistanceImpact)

Default impacts:

• armorImpact = 1.0
• toughnessImpact = 0.1
• knockbackResistanceImpact = 1.0

Armor provides the item's base weight. Toughness and Knockback Resistance multiply that base because those secondary defensive stats become more valuable when combined with Armor. The weights of all equipped pieces are then added together.

If two items have the same secondary stats and one provides twice as much Armor, it also weighs twice as much. An item with no Armor has zero weight even if it provides one of the secondary stats.

How weight becomes slowdown

Let W be total equipped weight and C be the player's effective Armor Weight Capacity:

overload = max(0, W - C)

Only overload is penalized. For half-speed overload H and curve exponent E:

remainingSpeed = 1 / (1 + (overload / H) ^ E)

Default values:

• baseArmorWeightCapacity = 20
• overloadForHalfSpeed = 42
• overloadCurveExponent = 1.5

H is a direct balance anchor: when overload reaches 42, the player retains exactly 50% movement speed. With the default capacity, this occurs at total weight 62.

E controls the curve shape:

• E = 1.0 produces a basic hyperbolic curve.
• Values above 1.0 make light overload gentler and heavy overload steeper.
• Values between 0 and 1.0 make light overload more punishing.

The optional maximum-slowdown limit is disabled by default, allowing extremely heavy armor to approach complete immobility. Servers can enable the limit and choose its value. The default configured value is 0.8, which caps the penalty at 80% and leaves at least 20% movement speed.

Optional Max Health scaling

Servers can optionally scale base Armor Weight Capacity using the player's effective Max Health. This feature is disabled by default, so installing the mod does not automatically connect health progression to armor balance.

Let M be effective Max Health, R be reference Max Health, and I be scaling impact:

capacityScale = max(0, 1 + (M / R - 1) * I)

Default values:

• enableMaxHealthCapacityScaling = false
• referenceMaxHealth = 20
• maxHealthScalingImpact = 1.0

The impact controls how strongly percentage changes in Max Health affect base capacity:

• I = 0 disables the effect of Max Health changes.
• I = 0.5 applies half of the Max Health percentage change.
• I = 1.0 scales capacity in direct proportion to Max Health.
• I = 2.0 applies twice the percentage change.

For example, with base capacity 20, reference Max Health 20, and effective Max Health 40, an impact of 0.5 produces base capacity 30, an impact of 1.0 produces 40, and an impact of 2.0 produces 60.

The calculation uses effective Max Health, so vanilla Health Boost and compatible modded health attributes work automatically. Scaling is applied as a transient multiply-base modifier on armor_weight:armor_weight_capacity, allowing other mods to add their own capacity modifiers without being overwritten.

Tooltips

Armor items with positive weight receive a vanilla-style tooltip line:

+3 Armor Weight

The normal tooltip also tells the player to hold Alt for more information. Holding Alt keeps the item-weight line visible and adds a projected summary:

16/20 Armor Weight
-0% Speed

The preview accounts for the item currently equipped in the same slot, showing the result of replacing that item rather than adding both weights.

Weight and capacity are blue while within capacity and red when overloaded. The speed line is blue at 0% and red when a slowdown applies.

Tooltip visibility can be disabled in the client configuration.

Movement integration

The slowdown is applied as a transient Movement Speed attribute modifier rather than a Slowness status effect.

The mod also scales the additional horizontal impulse created by vanilla sprint-jumping. This prevents sprint-jumping from bypassing armor weight without scaling the player's existing momentum twice.

Weight is recalculated when armor is equipped, removed, or replaced, and on login, respawn, and server configuration application. Cached equipment weight is not recalculated every tick.

Armor Weight Capacity is a synchronized player attribute named armor_weight:armor_weight_capacity. Its effective value is checked every server tick, so other mods can raise or lower capacity through ordinary attribute modifiers without forcing the player to re-equip armor.

Temporary skills, status effects, and modifiers applied directly to other player attributes do not change item weight. Only the attributes provided by equipped armor items are evaluated.

Configuration

Server-controlled gameplay settings:

• armorImpact
• toughnessImpact
• knockbackResistanceImpact
• baseArmorWeightCapacity
• enableMaxHealthCapacityScaling
• referenceMaxHealth
• maxHealthScalingImpact
• overloadForHalfSpeed
• overloadCurveExponent
• enableMaximumSlowdown
• maximumSlowdown
• affectSprintJumpImpulse

Client setting:

• showItemWeightTooltip

Gameplay settings required for movement prediction and item-weight previews are synchronized to connected clients. Effective Armor Weight Capacity is synchronized through Minecraft's attribute system, keeping displayed capacity and slowdown consistent with the server.

Mod compatibility

Armor using standard additive Armor, Armor Toughness, and Knockback Resistance attributes is supported automatically, including equipment from other mods.

ITM's Armor Weight has no required dependency on the other ITM movement mods:

• Sprint Equalizer works with Armor Weight's Movement Speed modifier and sprint-jump adjustment.
• Aerial Dash reads the resulting Movement Speed, so heavier armor reduces dash distance when horizontal Movement Speed scaling is enabled.

These integrations use vanilla attributes and movement behavior rather than direct mod dependencies.

Installation and requirements

Supported platforms:

• Minecraft 1.20.1 - Forge
• Minecraft 1.21.1 - NeoForge
• Minecraft 26.1.2 - NeoForge
• Minecraft 26.1.2 - Fabric

Install the file matching both your exact Minecraft version and mod loader.

The mod must be installed on both the client and server. In singleplayer, installing it in the normal client mod folder covers both sides.

Fabric installations also require Fabric API.

Modpacks

You may include the unmodified mod in public or private modpacks without asking for permission.

Armor Weight is distributed under the Apache License 2.0.