Flat bonuses (2d10 + 5)

At the table

You roll 2d10, then add a flat +5 from a stat or spell—every possible total goes up by 5. Games usually write that as 2d10 + 5.

Try it

In the playground, open this lesson in the playground and click Run (or press Shift+Enter).

The script

↗roll = 2d10
output("roll_base", roll)
output("roll_plus_5", roll + 5)

roll_base · DieRoll · mean 11.000

outcome	%	frac	X/100
2	1.00	1/100	1
3	2.00	1/50	2
4	3.00	3/100	3
5	4.00	1/25	4
6	5.00	1/20	5
7	6.00	3/50	6
8	7.00	7/100	7
9	8.00	2/25	8
10	9.00	9/100	9
11	10.0	1/10	10
12	9.00	9/100	9
13	8.00	2/25	8
14	7.00	7/100	7
15	6.00	3/50	6
16	5.00	1/20	5
17	4.00	1/25	4
18	3.00	3/100	3
19	2.00	1/50	2
20	1.00	1/100	1

roll_plus_5 · DieRoll · mean 16.000

outcome	%	frac	X/100
7	1.00	1/100	1
8	2.00	1/50	2
9	3.00	3/100	3
10	4.00	1/25	4
11	5.00	1/20	5
12	6.00	3/50	6
13	7.00	7/100	7
14	8.00	2/25	8
15	9.00	9/100	9
16	10.0	1/10	10
17	9.00	9/100	9
18	8.00	2/25	8
19	7.00	7/100	7
20	6.00	3/50	6
21	5.00	1/20	5
22	4.00	1/25	4
23	3.00	3/100	3
24	2.00	1/50	2
25	1.00	1/100	1

Remember: + between two dice expressions (for example 1d6 + 1d6, same as 2d6) means independent dice summed, not a flat modifier. A plain number on the right—+ 5, + STAT—is the tabletop-style bonus.

Try this

In the editor, change 5 to your game’s typical modifier.
Re-run and compare means: the bonus roll’s mean should equal the base mean + modifier.
Compare roll + 5 and shift(roll, 5)—means should match.