Apps like d20 Attack Calculator

Here are some great alternatives to d20 Attack Calculator by Hapero.fi :
Dicely – Dice Roller for DnD
Dicely – Dice Roller for DnD
★4.0
RPG Dice Roller
RPG Dice Roller
★5.0
RPG Dice Roller
RPG Dice Roller
★4.8
Mighty Dice
Mighty Dice
★4.6
Risk Battle Simulator
Risk Battle Simulator
★4.5
WH40K: Dice Companion (Pro)
WH40K: Dice Companion (Pro)
★4.5
DnDice - 3D RPG Dice Roller
DnDice - 3D RPG Dice Roller
★4.3
Xd6 - Dice Roller
Xd6 - Dice Roller
★3.7
RollHammer: Battle Dice
RollHammer: Battle Dice
★4.5
Delve: through the dungeons
Delve: through the dungeons
★3.3
D&D Beyond
D&D Beyond
★4.6
Game Master 5th Edition
Game Master 5th Edition
★4.0
MathHammer 40k
MathHammer 40k
★4.5
Rollplay - Character Sheet
Rollplay - Character Sheet
★3.8
Dice Roller: Roll, shift, save
Dice Roller: Roll, shift, save
★3.2
Dice vs Monsters: Roguelike TD
Dice vs Monsters: Roguelike TD
★3.6