Chiller Tonnage Calculator (CHW Plant Sizing)
Instant chiller sizing: Tons = GPM × ΔT (°F) × 500 ÷ 12,000. Example: 480 GPM × 10 °F → 200 TR (×1.15 SF ≈ 230 TR). Industrial chilled-water plant screen—not residential AC shopping.
Last reviewed:
Quick Calculator
Defaults: 480 GPM · 10 °F ΔT · SF 1.15. Results update instantly.
Advanced — safety / redundancy
About this calculator
Industrial CHW plant tonnage screen after you know cooling load from the HVAC size calculator. Browse all HVAC tools on the HVAC Calculators hub. Not OEM chiller selection, IPLV modeling, or glycol corrections.
Quick reference — GPM × ΔT → tons
| GPM | ΔT (°F) | Base tons | With SF 1.15 |
|---|---|---|---|
| 240 | 10 | 100 | 115 |
| 480 | 10 | 200 | 230 |
| 720 | 10 | 300 | 345 |
| 200 | 12 | 100 | 115 |
At 10 °F ΔT, ~2.4 GPM/ton. Raising ΔT reduces flow for the same tons (and vice versa).
How big is a 20 / 50 / 300 ton chiller? (PAA)
Physical footprint and electrical load vary by OEM. Use these planning anchors only—confirm submittals for length/width/kW.
| Nominal tons | ~GPM @ 10 °F ΔT | ~BTU/h | Planning note |
|---|---|---|---|
| 20 TR | ~48 GPM | 240,000 | Small process / rooftop CHW |
| 50 TR | ~120 GPM | 600,000 | Light commercial plant |
| 120 TR | ~288 GPM | 1,440,000 | Common mid-plant module |
| 300 TR | ~720 GPM | 3,600,000 | Large plant / N+1 bank |
Formula & explanation
Tons = GPM × ΔT (°F) × 500 ÷ 12,000 (equivalently GPM × ΔT ÷ 24).
From load: Tons = BTU/h ÷ 12,000, then multiply by your documented safety factor.
Best for: industrial / commercial CHW plant concept screens, process chillers with known flow and temperatures.
Not ideal for: residential SEER shopping, Manual J room loads alone, glycol systems without property corrections, or OEM IPLV / part-load selection.
Start facility load on HVAC capacity; psychrometrics on psychrometric calculator; plant kW screen via energy estimator / factory load. Browse the full set on the HVAC calculators hub.
Last updated: 2026-07-29. Screening estimate only—confirm OEM selection software for IPLV and glycol.
References
Worked example
Process loop: 480 GPM, supply–return 10 °F, planning SF 1.15.
- Base tons = 480 × 10 × 500 ÷ 12,000 = 200 TR
- With SF: 200 × 1.15 = 230 TR
- At 10 °F ΔT check: 230 × 2.4 ≈ 552 GPM if you size flow from tons instead
Next: confirm building/process load with HVAC size, then electrical demand on the plant bus.
FAQ
How to calculate chiller size (tonnage)?
For water: Tons = GPM × ΔT (°F) ÷ 24 (same as ×500÷12,000). Or Tons = BTU/h ÷ 12,000 from a known load. Apply a documented safety factor, then confirm OEM selection software.
How to calculate tonnage for a chiller vs HVAC capacity?
This page is chiller plant tonnage from CHW flow/ΔT. Building/zone HVAC capacity lives on the HVAC capacity calculator—screen load there first, then size the chiller here.
What size chiller for a 200 gallon tank?
Tank gallons alone do not set tons—you need heat load (BTU/h) or process flow and ΔT. A 200 gallon hold-up tank is a buffer volume, not a capacity rating.
Is this also a water chiller sizing / TR calculator?
Yes. Searches for chiller sizing calculator, water chiller tonnage, and chiller TR formula land here. Glycol loops need property corrections—this screen assumes water unless you adjust load inputs.
How do you calculate chiller tonnage from GPM?
Tons = GPM × ΔT (°F) × 500 ÷ 12,000. Example: 480 GPM × 10 °F → 200 tons before safety factor.
What is the difference between chiller tons and HVAC capacity tons?
HVAC capacity screens facility/zone load intensity. This page screens CHW plant capacity from flow and ΔT (or a known plant load).
How much GPM per ton of chiller?
At 10 °F ΔT, about 2.4 GPM/ton. Different ΔT changes the ratio.
Should I oversize the chiller by 20%?
Prefer an explicit, documented factor (and N+1 studies) over a blank 20%. Oversizing can hurt part-load efficiency.
Does this replace manufacturer software?
No. Use OEM selection for evaporator/condenser conditions, glycol, IPLV, and electrical data.