Cremation may serve as a funeral or postfuneral rite that is an alternative to the interment of an intact body in a casket. Cremated remains, which are not a health risk, may be buried or immured in memorial sites or cemeteries, or they may be legally retained by relatives or dispersed in a variety of ways and locations.

In many countries cremation is usually done in a crematory (or crematorium), but others may prefer different methods. An example is the common practice of open-air cremation in India.

The cremation occurs in a crematory (or crematorium), consisting of one or more cremator furnaces or cremation retorts for the ashes. A cremator is an industrial furnace capable of generating temperatures of 870–980 °C (1,598–1,796 °F) to ensure disintegration of the corpse. A crematorium may be part of chapel or a funeral home, or part of an independent facility or a service offered by a cemetery.

Modern cremator fuels include natural gas and propane. However, coal and coke were used until the early 1960s.

Modern cremators have adjustable control systems that monitor the furnace during cremation. These systems automatically monitor the interior to tell when the cremation process is complete, after which the furnace shuts down automatically. The time required for cremation thus varies from body to body, and in modern furnaces may be as fast as one hour per 45 kilograms (99 lb) of body weight.

A cremation furnace is not designed to cremate more than one body at a time, something that is illegal in many countries, including the U.S. Exceptions are sometimes made in extreme cases, such as of a deceased mother and her still-born child or still-born twins, but in these cases the mother and child must be placed in the same cremation container.

The chamber where the body is placed is called the retort and is lined with heat-resistant refractory bricks. The coffin or container is inserted (charged) into the retort as quickly as possible to avoid heat loss through the top-opening door. The container may be mounted on a charger (motorized trolley) that can quickly insert the container or on a fixed or movable hopper that allows the container to slide into the cremator.

Modern cremators are computer-controlled to ensure legal and safe use. For example, the retort door cannot be opened until the cremator has reached its operating temperature, and United States federal regulations require that newly constructed cremators feature dual electrical and mechanical heat shutoff switches and door releases accessible from inside the retort. Refractory bricks are typically replaced every five years because thermal fatigue gradually introduces fissures reducing their insulating strength.

Some crematoria allow relatives to view the charging. This is sometimes done for religious reasons, such as in traditional Hindu and Jain funerals.

Most cremators are a standard size. Typically, larger cities have access to an oversize cremator that can handle deceased in the 200 kilograms (440 lb)+ range. Most large crematoria have a small cremator installed for the cremation of fetal and infant remains.