How to calculate per diem for a trip, one day at a time

Take a hypothetical Monday–Wednesday trip in October 2026 to a location where the standard CONUS rate applies. Assume more than 12 hours away on official business, two eligible hotel nights, no personal days and no meals supplied by the government or a registration fee.

FY2027 supplies the rates: $113 per night and $68 per full meal day. Monday and Wednesday receive 75% of $68, or $51 each. Tuesday receives $68. The meal estimate is therefore $170.

At the nightly ceiling, the room budget is 2 × $113 = $226. Add $170 of meals to obtain a $396 planning ceiling, before lodging taxes or other transport costs.

If the eligible room costs $95 per night instead, estimated lodging is $190 and the combined estimate is $360. The $36 difference is unused room allowance; it does not increase the meal allowance. Entering an actual room price of zero correctly makes lodging zero.

A stay across a month boundary can use two different nightly ceilings. October 1 can also switch the fiscal-year edition. The calculator evaluates each date separately and shows the source year beside the trip summary.

After calculating, mark deductible provided meals on the specific dates. Download the daily CSV to retain the inputs and arithmetic. Keep your authorization and supporting documents separately: the CSV is a planning record, not an official travel voucher.