Dice Notation Explained: How to Read d20, 2d6, and 4d6 Drop Lowest

By the Super Simple Digital Tools Team · Updated June 2026 · Online Utilities

If you have ever opened a game rulebook and seen instructions like "deal 2d6+3 damage" or "roll 4d6, drop the lowest," you have met dice notation, a compact shorthand that has been standard in tabletop gaming since the mid-1970s. Once you can read it, a virtual dice roller becomes a drop-in replacement for any set of physical dice the rules demand, no matter how many or how many sides.

The core pattern is nds: the number of dice, the letter d, then the number of sides. A d6 is the familiar cube; polyhedral sets add the d4, d8, d10, d12, and the iconic d20, plus the d100 for percentages, usually rolled as two ten-sided dice. So 3d8 means roll three eight-sided dice. When you see just d20 with no leading number, the one is implied: it means a single die.

Two common add-ons change the result. A plus or minus modifier, as in 1d20+4, tells you to roll the die and then adjust the total by a fixed amount; the modifier itself never varies. A keep or drop instruction, written as 4d6 drop lowest (sometimes 4d6-L), tells you to roll more dice than you keep and discard the worst, which nudges the average upward. Character-creation rules lean on this trick to produce stronger, less swingy scores.

Knowing the math behind a roll helps you read the odds rather than just the numbers. A single die is flat: every face on a d6 has the same one-in-six chance. The moment you add dice and sum them, the distribution bunches toward the middle, because more combinations land there. Two six-sided dice peak hard at 7 and taper to the rare 2 and 12, forming a triangle; add a third die and the curve smooths into a bell shape centred near the average.

To reproduce any notation here, translate it into the roller's two settings. For 2d6+5, set the dice count to two and sides to six, roll, then add five to the shown total. For 4d6 drop lowest, set four dice of six sides, roll, and ignore the smallest result. For percentile checks, use a d100 or roll two d10 and read one as tens. With those moves you can run almost any tabletop encounter without owning a single physical die.

Quick tips

• When the notation has no leading number, like d12, treat it as 1d12: a single die of that many sides.
• Read +c and -c as fixed math applied after the roll, never as an extra die, so 1d8+2 always adds exactly two.
• For 4d6 drop lowest, roll four six-sided dice and discard the smallest to bias the result toward higher totals.
• To simulate a d100, either pick a 100-sided die or roll two ten-sided dice and treat one as the tens place.

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