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IV Drip Rate Calculator

Converts an infusion volume and duration into a gravity drip rate in drops per minute for a given tubing drop factor, and the equivalent pump rate in mL per hour.

When to use

You need to set a gravity infusion (macrodrip 10, 15 or 20 gtt/mL, microdrip 60 gtt/mL) or an infusion pump for a given volume over a given time.

Do not use when: The medication needs a weight-based dose first (use dose-by-weight) or the infusion is controlled by a syringe driver in mL/h with a dose-rate unit.

Formula

drops_per_minute = volume_ml × drop_factor_gtt_per_ml / duration_minutes; ml_per_hour = volume_ml / (duration_minutes / 60)

Gravity drip rates are approximate: drop size varies with fluid viscosity and set design, and the rate must be rechecked as bag height and venous pressure change. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Unit	Required	Description
`volume_ml`	number	mL	yes	Total volume of the infusion. Range: > 0, ≤ 20000
`duration_minutes`	number	min	yes	Time over which the volume is to run (hours × 60). Range: > 0, ≤ 10080
`drop_factor_gtt_per_ml`	number	gtt/mL	default 20	Drops per mL printed on the giving set: 10, 15 or 20 for macrodrip, 60 for microdrip. Range: ≥ 1, ≤ 100

Outputs

Output	Type	Unit	Description
`drops_per_minute`	number	gtt/min	volume × drop factor / minutes.
`drops_per_minute_rounded`	integer	gtt/min	Nearest whole drop per minute, as set at the bedside.
`ml_per_hour`	number	mL/h	volume / hours.
`seconds_per_drop`	number	s	60 / drops per minute.
`duration_hours`	number	h	Infusion time in hours.

Example

1000 mL over 8 h, 20 gtt/mL: {"volume_ml":1000,"duration_minutes":480,"drop_factor_gtt_per_ml":20} → {"drops_per_minute":41.7,"drops_per_minute_rounded":42,"ml_per_hour":125,"duration_hours":8}

100 mL over 30 min, microdrip 60 gtt/mL: {"volume_ml":100,"duration_minutes":30,"drop_factor_gtt_per_ml":60} → {"drops_per_minute":200,"ml_per_hour":200,"seconds_per_drop":0.3}

GET https://tttkmbb.com/api/v1/calculate/iv-drip-rate?volume_ml=1000&duration_minutes=480&drop_factor_gtt_per_ml=20

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/iv-drip-rate (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/iv-drip-rate · Markdown: https://tttkmbb.com/medical/iv-drip-rate.md · JSON definition: https://tttkmbb.com/medical/iv-drip-rate.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="iv-drip-rate"
OpenAPI operationId: calculate_iv_drip_rate
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Craker M, Janke C (2024) Nursing Dosage Calculations (open textbook, WisTech Open) (textbook)
Wikipedia – Drop (unit): IV drop factors (reference)

FAQ

Why does microdrip give the same number as mL/h?

With 60 gtt/mL, drops per minute equal mL per hour (60 drops/mL × mL/h ÷ 60 min/h), which is why microdrip sets are used for precise low-volume infusions.

Should I round the drip rate?

Yes, to the nearest whole drop per minute; count drops for a full minute (or 15 s × 4) when setting the roller clamp.

Related calculators

Dose by Weight Calculator — Calculate the dose and volume before setting the rate.
Maintenance Fluids Calculator — Hourly maintenance volumes to infuse.