Regarding Experience in 5th Edition (a helpful chart)

The following numbers are based on the Character Advancement chart on page 10 of the Player's D&D Basic Rules pdf, the Experience Points by Challenge Rating chart on page 5 of the DM's Basic Rules pdf, and the XP per Adventuring Day per Player Character chart on page 58 of that document.

For the sake of simplicity, the Encounters per Level assumes a party size of 1 and all encounters are CR = Character Level.

Character level	XP Required	XP to Advance	Recommended XP per Adventuring Day	Days to Level
1	0	300	300	1.00
2	300	600	600	1.00
3	900	1800	1200	1.50
4	2700	3800	1700	2.24
5	6500	7500	3500	2.14
6	14000	9000	4000	2.25
7	23000	11000	5000	2.20
8	34000	14000	6000	2.33
9	48000	16000	7500	2.13
10	64000	21000	9000	2.33
11	85000	15000	10500	1.43
12	100000	20000	11500	1.74
13	120000	20000	13500	1.48
14	140000	25000	15000	1.67
15	165000	30000	18000	1.67
16	195000	30000	20000	1.50
17	225000	40000	25000	1.60
18	265000	40000	27000	1.48
19	305000	50000	30000	1.67
20	355000	NA	40000	NA
			Total Time to level 20:	33.36 Days

Character level	XP Required	XP to Advance	XP by CR (where CR = Level)	Encounters per level
1	0	300	200	1.50
2	300	600	450	1.33
3	900	1800	700	2.57
4	2700	3800	1100	3.45
5	6500	7500	1800	4.17
6	14000	9000	2300	3.91
7	23000	11000	2900	3.79
8	34000	14000	3900	3.59
9	48000	16000	5000	3.20
10	64000	21000	5900	3.56
11	85000	15000	7200	2.08
12	100000	20000	8400	2.38
13	120000	20000	10000	2.00
14	140000	25000	11500	2.17
15	165000	30000	13000	2.31
16	195000	30000	15000	2.00
17	225000	40000	18000	2.22
18	265000	40000	20000	2.00
19	305000	50000	22000	2.27
20	355000	NA	25000	NA
			Total Encounters to level 20:	50.52

5th Edition. Because no epic adventure should take longer than a month...

Just don't tell Mr. Tolkien...