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Diaphragm vs External Condom

A side-by-side comparison of two birth control methods — efficacy, cost, how they work, and who shouldn't use them.

Last verified October 11, 2026Updated October 11, 2026

Side-by-side comparison

Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.
External Condom A barrier method worn over the penis that also lowers the risk of STIs, available over the counter.

Method	Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.	External Condom A barrier method worn over the penis that also lowers the risk of STIs, available over the counter.
Efficacy	Diaphragm 83% typical use Least effective: under 90 out of 100 people successfully prevent pregnancy per year.	External Condom 87% typical use Least effective: under 90 out of 100 people successfully prevent pregnancy per year.
Cost	Diaphragm $0–$250 Insurance: Usually	External Condom $0–$2 per unit Insurance: Varies
Duration	Diaphragm Reusable for up to 2 years (replace sooner if damaged)	External Condom Single use
Reversibility	Diaphragm Reversible	External Condom Reversible
STI protection	Diaphragm No	External Condom Yes
How it works	Diaphragm A reusable silicone dome covers the cervix to block sperm from reaching an egg. Used with spermicide for added effectiveness.	External Condom A sheath worn over the penis that keeps sperm from entering a partner's body. Latex and plastic condoms also block contact with semen and vaginal fluids that can carry STIs.
Prescription	Diaphragm Required Hybrid (Fitting or Ship)	External Condom Not required Over-the-Counter
Side effects	Diaphragm Increased risk of urinary tract infection Vaginal irritation from spermicide Toxic shock syndrome risk (rare)	External Condom Allergic reaction to latex in people with a latex allergy
Who shouldn't use this	Diaphragm Uterine or cervical anomaly preventing fit Sensitivity to silicone or spermicide Inability to insert or remove reliably History of toxic shock syndrome High risk of HIV exposure (because of the spermicide)	External Condom Known allergy to latex (use polyisoprene or polyurethane instead)

Key differences

With typical use, 17 in 100 people using Diaphragm get pregnant in a year, vs 13 in 100 with External Condom (both least effective). How long it lasts: Diaphragm, reusable for up to 2 years (replace sooner if damaged); External Condom, single use. STI protection: only with External Condom. A prescription is needed for Diaphragm, not for External Condom. Diaphragm: costs $0–$250. External Condom: costs $0–$2 per unit.