Block Strength

Block Strength is a vanilla mechanic that determines how fast a block can be broken by the player, it is affected by Tool Speed and Haste on a private island and by on a public island.

For more information on how it works in the vanilla game and on private islands, see the official page on the Minecraft Wiki.

SkyBlock Behavior
While mining, is dealt as damage to the block every tick. When enough damage is dealt, the block will break, dropping an item and turning into bedrock (outside of Crystal Hollows) for a few seconds.

If is high enough, the block will be mined instantly.

Otherwise, damage is limited to 7.5x a block's strength, limiting the break time to 4 ticks (or 0.2s). This is known as a block's Softcap.

Formula
To determine the time to break a block we can use this formula. In the formula below, Mining Time is measured in ticks, where 1 tick is 0.05s. It is rounded to the nearest integer.

$$\text{Mining Time}=\left\lfloor\frac{\text{Block Strength}\times 30}{\text{Mining Speed}}\right\rceil$$

To get the time in seconds, divide the result by 20.

Softcap
Softcap limits how fast a block can be mined to at least 4 ticks (or 0.2s). To determine the mining speed needed to hit the softcap of a given block, use the following formula:

$$\text{Softcap}=\left\lceil{\frac{20}{3}\left(\text{Block Strength}\right)}\right\rceil$$

The softcap can be bypassed by breaking a block instantly.

Instant Mining
The softcap can be bypassed if the block is mined within a single Minecraft tick (0.05s). In this case, the block will break instantly.

To instantly break a block, mining speed needs to be 30x higher than a block's strength, or 60x if it's an ore.

Calculators
Note: this is the base amount of ticks, the real amount of ticks might be +1-2 or more depending on your ping