PROBLEM TO BE SOLVED: To provide an estimation system and others capable of reducing the effect of variation (increase/decrease) of gas consumption used by a consumer, and increasing the credibility of estimation and calculation of the gas consumption.SOLUTION: A server includes: a reception unit that receives indicator data including meter indicator values detected by a first gas meter from the gas meter for detecting total consumption of gas delivered collectively to and used by a plurality of first consumers; a calculation unit that calculates a previous day ratio of gas consumption used per day to be calculated based on the meter indicator values included in the indicator data; a storage unit that stores a gas residual amount in a gas container of a second consumer different from the first consumers; and an update unit that calculates a future gas consumption per day to be consumed by the second consumer on the basis of the previous day ratio of gas consumption, and updates the gas residual amount in the
