Charts

15 Amp vs 20 Amp Receptacles: How to Tell Them Apart

Look at the slots with the ground at the top or bottom. Two vertical slots side by side and a ground: 15 amperes, NEMA 5-15R. One vertical slot, one T-shaped slot and a ground: 20 amperes, NEMA 5-20R. The T is the neutral. Both are 125 volts. If a plain slot runs horizontal, the device is 250 volts: see the 250 volt pair below.

Answers

Is this a 15 A or a 20 A receptacle, and which one may go on this circuit?

Format

Selection guide

Sources

23 cited

Last checked

October 1, 2026

The plugs mirror the slots. Hubbell: a 5-15P has two vertical blades and a ground; a 5-20P has one vertical blade, one horizontal blade and a ground. A 5-20P goes only into a 5-20R. Both receptacles take a two-blade 1-15P.⁵

The rating is also on the device. Leviton states ratings are permanently marked on the device. If the face and the marking disagree with what you expected, believe the marking.¹⁷

The two tables that settle it

OSHA’s general industry electrical standard carries both rules as tables. The NEC’s Table 210.21(B)(2) and Table 210.21(B)(3) carry the same values in the 2005 text posted by one Illinois village, and North Carolina’s fire marshal office applies the receptacle table under its 2014 Electrical Code.^{1 12 13}

Table S-5 applies where the circuit supplies two or more receptacles or outlets. The construction standard repeats it as Table K-4 in 29 CFR 1926.404. A single receptacle on an individual branch circuit must have an ampere rating not less than that of the branch circuit.^{1 4}

Confirm the circuit before you spec the device

• The breaker. UL: circuit breakers are marked with their ampere rating.⁷
• The conductor. Encore Wire prints the NEC small conductor rule: unless specifically permitted in 240.4(E) through (G), overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG and 30 amperes for 10 AWG copper.²²
• The cable jacket, as a first look only. NEMA: NM-B cable has been made with color-coded jackets since 2001. White is 14 AWG copper, yellow is 12 AWG, orange is 10 AWG.²⁰
• Then read the print. NEMA says the color code is voluntary and the print legend is what verifies conductor size. Its 2023 revision also assigns white to 12 AWG copper-clad aluminum, and Cerrowire’s three-conductor cables use light blue, purple and pink. Color alone proves nothing.^{20 21}

Where dwelling circuits must be 20 A

A 20 A circuit does not require 20 A receptacles. See Table S-5.

The 250 volt pair

Same idea one series up. 6-15R is 15 A, 250 V. 6-20R is 20 A, 250 V and carries the T slot. OSHA’s allowance is written for both voltages: a 20 ampere T-slot receptacle may accept a 15 ampere attachment plug of the same voltage rating.^{18 2}

Other marks on the face

What not to do

• No 20 A receptacle on a 15 A circuit that supplies two or more receptacles or outlets. A duplex is two. Table S-5: not over 15 A.¹
• No single 15 A receptacle as the only receptacle on a 20 A individual circuit.^{1 15}
• No load over 12 A on a 15 A receptacle or 16 A on a 20 A receptacle.¹
• No push-in terminations on a 20 A circuit or with 12 AWG wire. UL restricts push-in terminals to 15 A branch circuits and 14 AWG solid copper.⁷
• No standard receptacle on aluminum branch wiring. CPSC on aluminum wiring repairs: hire a qualified electrician, do not try to do it yourself, and treat CO/ALR devices as at best an incomplete repair.^{7 23}

Sources

1. OSHA. 29 CFR 1910.304(b)(4), Wiring design and protection: outlet devices, Table S-4 and Table S-5. eCFR, current as of September 30, 2026.
2. OSHA. 29 CFR 1910.305(j)(2)(ii), receptacles, cord connectors and attachment plugs. eCFR, current as of September 30, 2026.
3. OSHA. 29 CFR 1910.399, Definitions applicable to this subpart: Receptacle. eCFR, current as of September 30, 2026.
4. OSHA. 29 CFR 1926.404(b)(2), outlet devices, Table K-4 (construction). eCFR, current as of September 30, 2026.
5. Hubbell Wiring Device-Kellems. Frequently Asked Questions. Read October 1, 2026.
6. Hubbell Wiring Device-Kellems. NEMA Straight Blade Devices (catalog configuration chart). 2017.
7. UL. Guide Information for Electrical Equipment: The White Book 2015-16, categories RTRT (receptacles) and DIVQ (circuit breakers). 2015.
8. Leviton. Captain Code 2023: 406.3(D) receptacles with push-in terminals, reprinted from the 2023 NEC. 2023.
9. Leviton. Captain Code 2023: 406.12 tamper-resistant receptacle requirements. 2023.
10. Leviton. Captain Code 2023: 406.9(A)(B) receptacles in damp and wet locations. 2023.
11. Leviton. Captain Code 2017: 210.11(C)(4) garage branch circuits. 2017.
12. Village of Schiller Park, Illinois. Section 210 NEC 2005 (NFPA 70, 2005 edition, Article 210). 2005.
13. North Carolina Office of the State Fire Marshal. Interpretation: 15 Amp Duplex Receptacles on 20 Amp Circuits, Section 210.21(B)(3), 2014 Electrical Code. March 16, 2017.
14. City of Saint Paul, Minnesota. Residential Dwelling Checklist 2023 NEC (Rough-In). 2023.
15. Legrand. Knowledge base article 000006694: Can a 15A outlet work on a 20A circuit?. January 28, 2020.
16. Leviton. Instruction sheet: Tamper Resistant Outlet T5325. Undated.
17. Leviton. Product pages CR15-W (5-15R) and BR20-W (5-20R). Read October 1, 2026.
18. Leviton. Product pages 5661-W (6-15R) and 5821-W (6-20R). Read October 1, 2026.
19. Leviton. GFCI Product Bulletin: SmartlockPro Self-Test GFCIs. 2024.
20. National Electrical Manufacturers Association. Technical Services Department Bulletin No. 94: Type NM-B Cable Jacket Color Coding for Conductor Size Identification. Revised April 20, 2023.
21. Cerrowire. CerroMax NM-B Cable product page. Read October 1, 2026.
22. Encore Wire. Wire Ampacity Size Table. Read October 1, 2026.
23. U.S. Consumer Product Safety Commission. Repairing Aluminum Wiring, Publication 516. June 2011.