About this tool
The D&D 5e Spell Save DC, Attack Bonus & Encumbrance calculator handles a spellcaster's two key numbers and a fighter's carrying limits in one place. Enter your spellcasting ability score, your level and your Strength score, and it returns your spell save DC, your spell attack bonus, and the full set of Strength-based weight thresholds. It all runs locally in your browser.
Spell save DC = 8 + proficiency bonus + spellcasting-ability modifier, and spell attack bonus = proficiency bonus + spellcasting-ability modifier, where the ability modifier is floor((score − 10) / 2) and the proficiency bonus is 2 + floor((level − 1) / 4). So a level-5 caster (proficiency +3) with a spellcasting ability of 16 (+3) has a save DC of 14 and a +6 to spell attacks. Carrying capacity is Strength × 15 lb, and the maximum you can push, drag or lift is Strength × 30 lb.
The optional variant-encumbrance rules from the Player's Handbook are included: you are encumbered (speed −10 ft) once you carry more than Strength × 5 lb, and heavily encumbered (speed −20 ft, disadvantage on ability checks, attacks and saves that use Strength, Dexterity or Constitution) above Strength × 10 lb. Enter a current carried weight and the tool reports which band you fall into. Every weight is shown in pounds with a kilogram conversion (lb × 0.4536).